JP5287225B2 - Polypropylene resin film for surface protection and surface protection film - Google Patents

Description

  The present invention relates to a surface-protective polypropylene-based resin film and a surface protective film, and in particular, has high thermal deformation resistance and flatness at high temperatures, and is excellent in processing suitability such as adhesive processing, and an additive. The present invention relates to a surface-protective polypropylene-based resin film that is suitable for the surface protection of various articles, and a surface-protective film using the surface-protective polypropylene-based resin film. is there.

  Polypropylene-based unstretched films have good transparency and are inexpensive, and are therefore widely used as base materials for surface protection films for the purpose of protecting the surface of various packaging materials such as food packaging and various articles.

For example, even in the surface protection film field, a surface protection film is attached to the surface of a metal plate, decorative plate, resin plate, glass plate, etc. to prevent surface scratches, dirt and rust that tend to occur during transportation and processing. Method (for example, refer to Patent Documents 1 to 3), for example, scratches, dust adhesion, contamination during processing and assembly of electronic, precision products, components and related members such as related materials such as liquid crystal panels and polarizing plates As a coating surface protection film for protecting a coating film on an automobile body from acid rain, dust, dust, etc. during transportation and storage of the vehicle, for example, (For example, see Patent Documents 6 and 7, etc.) For example, as a method of partially plating the connection terminal portion of the flexible printed circuit board, an adhesive film is attached to the non-plated portion and the mask is used. Then, use in plating and etching processes such as a method of plating and a method of protecting a resist film or etching resistance film provided on an unetched surface in an etching process at the time of manufacturing a shadow mask (see, for example, Patent Documents 8 and 9) ), A method for protecting a surface of a semiconductor element by laminating a film on a surface without a circuit of the semiconductor element, and simplifying a process when assembling a semiconductor device (for example, see Patent Documents 10 and 11, etc.) Used in the field.
JP 2003-119435 A JP 2003-213229 A JP 2005-281328 A Japanese Patent Laid-Open No. 10-309781 JP-A-11-165368 JP-A-8-143829 Japanese Patent Laid-Open No. 2001-121661 JP-A-11-291411 Japanese Patent Laid-Open No. 11-302611 JP 2004-63551 A JP 2004-142430 A

  The surface protective film is generally used by laminating an adhesive layer on the surface of a base film and fixing it to the surface of an object to be protected using the adhesive force of the adhesive layer. In recent years, with the expansion of applications, demands for quality and cost reduction have become stronger, and there is a demand for a base film having excellent adhesive processability. In particular, for the purpose of increasing the processing speed of adhesive processing, etc., the processing temperature is increasing, and even when processed at a high temperature, thermal deformation due to the processing temperature is small and dimensional stability during processing is good, There is a demand for dimensional stability at high temperatures (hereinafter, also simply referred to as heat-resistant dimensional stability) that suppresses the occurrence of hot flame during processing.

  In addition, the polypropylene resin film contains minute foreign matter called fish eye. For example, the definition of fish eye is written in Polymer Editorial Board, Polymer Dictionary, Taiseisha, 2000, 6th edition, P337, etc. A fish eye refers to a small spherical shape or the like formed in a film product. The name was given because there are many things that have transparency like fish eyes. There are various types such as unmelted lumps resulting from insufficient kneading of the molding material, lumps due to gelation of a part of the raw material, lumps due to partial deterioration of the material during molding, and those with foreign matter as the core. The fish eye here excludes those with foreign matter as the core. Examples of the foreign matter include cellulose, dust, metal pieces, resin carbide, plastics of different types, lint, and pieces of paper. Even in protective film applications, the above-mentioned poor appearance deteriorates the product image of the protected product, so there is a strong demand for suppression of mixing. In particular, for example, in the case of a protective film for plating, if the fish eye is present, a protrusion is formed in a portion where the fish eye is present on the film, and adhesion failure occurs between the protrusion and an object to be protected. A space is created between the object and the object, and the plating solution enters the space and the protective effect is reduced. Therefore, it is necessary to reduce it as much as possible. In the case of a protective film for protecting the LCD panel, the fish eye on the surface of the protective film may be damaged by the unevenness or rubbing of the fish eye when pressed on the surface in contact with the LCD panel. That is a problem. Recently, liquid crystal plates have been inspected with a protective film for protecting the liquid crystal plate. If fish eyes are present, it may be determined that the liquid crystal plate itself is a defect. The development of films such as grades and low fish eye grades is required.

Also, a polypropylene-based resin film with a large amount of crystal nucleating agent added has been proposed for the purpose of improving the heat-resistant dimensional stability of the film (Patent Document 19). Since the residence time during extrusion of the resin becomes relatively long, there is an effect of improving the crystallinity when the resin is cooled, but fish eyes are generated due to aggregation and decomposition of the crystal nucleating agent in the film. Not practical.
Japanese Patent Application No. 2006-98227

In addition, a polypropylene resin composition containing a crystal nucleating agent and two kinds of antioxidants and a molded body formed by molding the same are disclosed (see Patent Documents 20 and 21).
JP 2000-109519 A JP 2000-248147 A

  In the technique disclosed in Patent Document 20, improvement of the heat distortion temperature is shown. Further, in the technique disclosed in Patent Document 21, the effect of improving impact resistance at low temperatures is shown. However, there is no mention of the effect that is the object of the present invention. For example, although fisheye is not mentioned at all, it is presumed that the above-mentioned high market demand for fisheye is not satisfied.

  The present invention is excellent in heat-resistant dimensional stability and flatness, excellent in impact resistance and bonding processability, has little fish eye and good transparency, for example, for surface protection suitable as a base film for a protective film An object of the present invention is to provide a protective film in which an adhesive layer is provided on a polypropylene resin film and the surface protecting polypropylene resin film.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.

That is, the present invention is a surface-protective polypropylene-based resin film having a polypropylene-based resin as a main component, the 20 ° C. xylene-soluble part amount is more than 9% and less than 16%, The addition is 100 ppm or less, the crystallinity of the film is 30 to 65%, and the birefringence (Δn) is 0.4 × 10 ^{−3 to} 2.5 × 10 ^−3. It is a polypropylene resin film.

  In this case, the thickness variation rate of the film is preferably ± 1 to 10%.

In this case, the content of the antiblocking agent in the film is preferably 50 ppm or less, and the blocking resistance is preferably 10 mN or less.

  In this case, the content of the lubricant in the film is preferably 50 ppm or less.

Furthermore, in this case, the number of fish eyes having a maximum diameter of 0.2 mm or more in the film is 0 / m ² and the number of fish eyes having a maximum diameter of less than 0.2 mm is 100 / m ² or less. Is preferred.

  Furthermore, in this case, the Young's modulus in the longitudinal direction at 23 ° C. of the film is preferably 500 Mpa or more.

  In this case, the impact strength of the film at 23 ° C. is preferably 0.3 J or more.

  Furthermore, the present invention is a surface protective film in which an adhesive layer is provided on at least one surface of the above-mentioned surface protective polypropylene resin film.

The present invention is excellent in heat-resistant dimensional stability and flatness, excellent in impact resistance and bonding processability, has few fish eyes, and has good transparency. For example, it is suitable as a base film for a protective film.
Since the polypropylene resin film for surface protection of the present invention is excellent in heat-resistant dimensional stability, for example, it is suitable for secondary processing such as adhesive processing, and is particularly subjected to treatment such as drying at a high temperature around 130 ° C. In addition, since the occurrence of hot stagnation and film sagging is suppressed, the productivity of the secondary processing can be improved, and the generation of defective products due to hot sag and film sagging can be suppressed.
Further, the present invention has small thickness spots.
Moreover, it is preferable that the polypropylene resin film of the present invention does not substantially contain an antiblocking agent. For example, when a film containing an antiblocking agent is run, the antiblocking agent falls off due to wear or the like. Therefore, the contamination and the occurrence of troubles due to the fallout are suppressed.
Moreover, it is preferable that the polypropylene resin film for surface protection of the present invention does not substantially contain a lubricant. For example, when used as a base film of a protective film, the lubricant is transferred to an article to be packaged or a body to be protected. Since there is no contamination, the contamination of these objects to be packaged and the objects to be protected is suppressed.
In addition, although the present invention does not substantially contain a lubricant or an anti-blocking agent, the surface roughness is appropriate, the slipperiness and blocking resistance of the film are good, and the film is excellent in rigidity. Is easy to handle.
Moreover, since it is excellent in transparency, it is excellent in the visibility of a to-be packaged object or a to-be-protected body.
In addition, because of the strength of the film, it is excellent in handleability.
In addition, despite its improved heat-resistant dimensional stability, it has excellent impact strength and maintains good impact resistance by being made of block polypropylene resin. High reliability when there is.

The polypropylene-based resin film of the present invention contains a polypropylene-based resin as a main component. Preferably, the film preferably contains 70% by weight or more of polypropylene-based resin, and more preferably 80% by weight or more.
The polypropylene resin used in the present invention can be used by mixing one or three of homopolypropylene resin, random copolymerized polypropylene resin copolymerized with ethylene and other α-olefins, and block copolymerized polypropylene resin. .
From the viewpoint of transparency, it is preferable to mainly use a homopolypropylene resin or a random copolymerized polypropylene resin copolymerized with ethylene or other α-olefin, in order to improve impact resistance and slipperiness, particularly blocking resistance. It is preferable to mainly use a block copolymerized polypropylene resin. The mixing ratio can be adjusted arbitrarily.

Although it does not specifically limit regarding the composition of said polypropylene resin, If it is a random copolymerization polypropylene resin, it is preferable that alpha-olefin content is 5% or less from the surface of heat-resistant dimensional stability. In addition, in the case of a block copolymerized polypropylene resin, a 20 ° C. xylene-soluble part amount is preferably 3 to 50% from the viewpoint of heat-resistant dimensional stability, slipperiness, and blocking resistance, and more preferably in the range of 5 to 30%. preferable.
The intrinsic viscosity of the whole polypropylene resin is 1.5 to 4.0, the intrinsic viscosity of the 20 ° C. xylene soluble part is 1.0 to 4.0, and the intrinsic viscosity of the 20 ° C. xylene insoluble part is 1.0 to 4. Those that are zero are preferred. The melt flow rate of the polypropylene resin used in the present invention is preferably 2 to 20 g / 10 min at 230 ° C.

  Further, a small amount of α-olefin random copolymer elastomer, ionomer, and other master batches may be added for various purposes.

  As the α-olefin random copolymer elastomer used in the present invention, ethylene-propylene, ethylene-butene, a propylene-butene binary system, an ethylene-propylene-butene ternary copolymer or a mixture thereof is used. Can be used. Moreover, you may use the copolymer which copolymerized another monomer in the range which does not impair the characteristic. In particular, the use of the above binary copolymer is preferable. In addition, it is preferable to use a laminate having a bigat softening point of 60 ° C. or lower and a surface hardness of 80 ° or lower from the viewpoint that a preferable elastic force can be imparted to the laminate.

The polypropylene resin film of the present invention needs to have a 20 ° C. xylene soluble part amount of more than 9% and less than 16%.
If it is 9% or less, the film is easily plastically deformed during high-temperature processing and is inferior in impact resistance. If it is 16% or more, the elastic film deformation rate index becomes large and the processability is inferior.
The lower limit of the 20 ° C. xylene soluble part is preferably 10% or more from the viewpoint of preventing whitening when the film is bent, and more preferably 15% or less from the viewpoint of the anti-blocking property of the film.

In the present invention, as described above, it is preferable not to add a lubricant or an anti-blocking agent that is carried out in a normal polypropylene resin film, but in that case, it is necessary to suppress deterioration of the slipperiness and blocking property of the film. is there. The correspondence is preferably carried out by the above-described resin composition, in particular, film surface protrusions with a sea / island structure made of a block copolymer resin or an ethylene copolymer elastomer.
At this time, it is preferable that it is 1-10 mN or less by the evaluation mentioned later as an anti-blocking characteristic of the film of this invention. More preferably, it is 1-7 mN or less.
On the other hand, the formation of film surface protrusions due to the sea / island structure with the block copolymer resin causes a decrease in transparency of the film. Therefore, in this method, the effect of improving slipperiness and blocking resistance due to the formation of surface protrusions and transparency Ensuring sex is a contradictory phenomenon. Therefore, the haze value of the film is an important factor.
Therefore, in the present invention, it is important to set the haze value of the film to 40% or less. 35% or less is preferable and 30% or less is more preferable. By setting the haze value to 40% or less, the visibility of the article to be packaged or the object to be protected is improved, and when used as a packaging bag material, the contents of the article to be packaged can be easily confirmed. Further, when used as a material for a surface protective film, for example, it is possible to inspect an object to be protected while the surface protective film is adhered. On the other hand, when the haze value exceeds 40%, the transparency is deteriorated and the visibility of the article to be packaged or the object to be protected is unfavorable. On the other hand, the lower limit of the haze value is preferable because the transparency is improved. However, 5% or more is preferable and 10% or more is more preferable in terms of imparting slipperiness by the above method.

  Moreover, it is preferable that the content of antiblocking agents, such as inorganic and / or organic microparticles | fine-particles, in the film for surface protection polypropylene resin films of this invention is 50 ppm or less. The content of the anti-blocking agent is more preferably 10 ppm or less, and particularly preferably the detection limit or less by a usual quantitative method such as ash or elemental analysis. That is, it is preferable not to contain an antiblocking agent substantially. Here, substantially not containing an antiblocking agent has the same meaning as in the case of the above-mentioned lubricant. By this measure, the anti-blocking agent is prevented from falling off due to film abrasion in the film production and secondary processing steps, so that contamination, troubles, and the like due to the fall-off are suppressed.

  The polypropylene resin film for surface protection of the present invention preferably has a content of a lubricant such as polyethylene wax, calcium stearate, erucic acid amide, ethylene biserucic acid amide in the film of 50 ppm or less. The content of the lubricant is more preferably 10 ppm or less, and particularly preferably the detection limit or less by a usual quantitative method such as elemental analysis or extraction method. That is, it is preferable that substantially no lubricant is contained. Here, “substantially containing no lubricant” means forming a film without positively adding the lubricant. The above range is to include that there is a case where a minute amount is mixed due to brand switching or the like at the time of manufacturing a raw material polymer or film without positively adding a lubricant, and it is a preferable embodiment that substantially does not contain a lubricant. is there. According to the countermeasure, the contamination of the protected object is prevented by the migration of the lubricant to the film surface and the subsequent transfer to the protected object in the method of adding the lubricant and improving the slipperiness of the film. Is retained.

The polypropylene resin film for surface protection of the present invention has a crystallinity of 34 to 65% by a measurement method described later. If the degree of crystallinity is less than 34%, the heat-resistant dimensional stability is difficult to be exhibited, and when processing in a later process is performed, the film is likely to be damaged or stretched, resulting in poor flatness. On the other hand, when the crystallinity exceeds 65%, the transparency of the film is remarkably deteriorated. On the other hand, if the crystallinity exceeds 65%, the Young's modulus increases and the suitability for bonding becomes worse.
The lower limit of the crystallinity of the film is more preferably 40% or more, and most preferably 50% or more from the viewpoint of heat-resistant dimensional stability. On the other hand, the upper limit of the crystallinity of the film is preferably 60% or less from the viewpoint of transparency.

  In addition, the surface-protective polypropylene resin film of the present invention is a polypropylene resin film that has reached a desired crystallinity (34 to 65%) by a production method even if it contains substantially no crystal nucleating agent. preferable. The manufacturing method may be achieved by raising the temperature of the cooling roll when the molten resin is taken and cooled and solidified, or by heat treatment (annealing).

  The polypropylene resin film for surface protection of the present invention can be added if the crystal nucleating agent is in the range of 100 ppm or less. By adding a crystal nucleating agent, the heat-resistant dimensional stability of the film can be improved. On the other hand, if the crystal nucleating agent is added in excess of 100 ppm, depending on the melt extrusion conditions of the resin, fish eyes in the film tend to increase, which causes a problem. Further, it is not preferable because a problem such as a reduction in productivity such as pressure increase due to clogging of a filter provided in an extruder for the purpose of removing foreign substances in the resin occurs. In addition, there is also a problem that crystallization proceeds when exposed to a high temperature even after becoming a product.

  Examples of the crystal nucleating agent include, but are not limited to, a crystal nucleating agent mainly composed of a metal salt of rosin, a sorbitol-based crystal nucleating agent, and a crystal nucleating agent composed of an aromatic organophosphate metal salt.

Moreover, the polypropylene resin film for surface protection of the present invention has a birefringence (Δn) of 0.4 × 10 ^{−3 to} 2.5 × 10 ⁻³ . When the birefringence is less than 0.4 × 10 ⁻³ , the film is likely to be damaged or stretched, and thus the flatness becomes poor and the heat-resistant dimensional stability is inferior. On the other hand, when the birefringence index exceeds 2.5 × 10 ⁻³ , the impact resistance is remarkably lowered and the mechanical properties of the film itself are deteriorated. From the viewpoint of maintaining heat-resistant dimensional stability and flatness, the birefringence of the film is preferably 0.6 × 10 ⁻³ or more, and more preferably 0.8 × 10 ⁻³ or more. On the other hand, from the viewpoint of maintaining the mechanical properties of the film, the birefringence of the film is preferably 2.3 × 10 ⁻³ or less, and more preferably 2.2 × 10 ⁻³ or less.

In the present invention, the elastic film deformation rate is preferably less than 7.0 × 10 ³ % · MPa.
The elastic film deformation rate referred to here is a value obtained by multiplying the deformation rate when the temperature is increased or decreased by applying a constant load in the flow direction of the film and the film elastic modulus in the flow direction at room temperature, more preferably 6 It is less than 0.0 × 10 ³ % MPa.
If the 20 ° C. xylene-soluble part amount is too small, or the crystallinity and birefringence are too large, the film elastic modulus becomes too large and the elastic film deformation rate is outside the preferred range. At this time, the film is plastically deformed and difficult to handle. On the other hand, if the 20 ° C. xylene soluble part amount is too large or the crystallinity and birefringence are too small, the deformation rate becomes too large and the elastic film deformation rate falls outside the preferred range. At this time, the dimensional stability of the film deteriorates during the adhesive processing.

  Moreover, the polypropylene resin film for surface protection of the present invention preferably has a thickness variation rate of 1 to 10%. When the thickness variation rate is less than 1%, there is no problem in terms of quality, but the time required for adjusting the thickness becomes enormous and the economic efficiency is remarkably lowered, which is not realistic. On the other hand, when the thickness variation rate exceeds 10%, the heat-resistant dimensional stability and transparency vary in proportion to the thickness variation, and the flatness of the film (waving and curling) is deteriorated, which is not preferable. The thickness variation rate is more preferably 1.5 to 8%, and most preferably in the range of 2 to 5%.

In the present invention, the polypropylene resin film for surface protection of the present invention preferably has 0 fisheye / m ² having a maximum diameter of 0.2 mm or more in the film. Further, the number of fish eyes having a maximum diameter of less than 0.2 mm is preferably 100 / m ² or less. The number of fish eyes having a maximum diameter of less than 0.2 mm is most preferably 0 / m ² or less, but the above range is preferable in view of economic efficiency and market demand. 2-80 pieces / m ² or less is more preferable, and 2-60 pieces / m ² or less is more preferable. In addition, the minimum diameter of the fish eye that can be visually determined is said to be 0.03 to 0.05 mm. By this correspondence, when it is used as a base film of a protective film, for example, when it is used as a base film of a protective film, it is possible to suppress the occurrence of troubles due to the penetration of the plating solution into the protective part due to the above-mentioned poor adhesion.

  The means for achieving the above characteristics is not limited, but the antioxidant may be optimally blended as described later.

  In the present invention, the polypropylene resin film for surface protection of the present invention preferably has a Young's modulus in the longitudinal direction at 23 ° C. of 500 Mpa or more. 680 Mpa or more is more preferable, and 720 Mpa or more is more preferable. If it is less than 500 Mpa, the handleability of the film is lowered, which is not preferable. By this measure, it is possible to suppress a decrease in the handleability of the film due to the absence of the above-mentioned lubricant or antiblocking agent. The upper limit is preferably about 1000 Mpa from the balance with other characteristics.

  In the present invention, the polypropylene resin film for surface protection of the present invention preferably has an impact strength at 23 ° C. of 0.3 J or more. 0.5J or more is more preferable. In general, when the rigidity and heat-resistant dimensional stability described above are improved, the impact strength moves in a decreasing direction. When the impact strength is reduced, the reliability of the impact resistance during use when used as a packaging bag, a protective film or the like is lowered. Therefore, it is preferable to satisfy the above-mentioned characteristics while giving the above-mentioned characteristics. The upper limit is preferably about 0.8 J from the balance with other characteristics.

  The method of imparting the impact strength is not limited, but is greatly affected by the amount of the 20 ° C. xylene soluble part. It is preferably achieved as the overall effect of the preferred embodiments described herein including the 20 ° C. xylene soluble part.

  In the present invention, it preferably comprises at least two antioxidants selected from at least one selected from acrylate antioxidants, phosphorus antioxidants and phenolic antioxidants. It is a more preferred embodiment that three types of acrylate antioxidant, phosphorus antioxidant and phenolic antioxidant are used in combination.

  The above three kinds of antioxidants are not limited to one type each. Two or more of each type may be used in combination, and in addition to the above three types of antioxidants, for example, an antioxidant having another structure such as a sulfur-based antioxidant may be further used in combination.

  The acrylate antioxidant of the present invention is an antioxidant having a phenol derivative containing an acrylate residue in the molecule. Examples of the acrylate compound include 2,4-di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate, 2,4-di-t. -Amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) butyl] phenyl acrylate, 2,4-di-t-amyl-6- [1- (3,5-di -T-amyl-2-hydroxyphenyl) propyl] phenyl acrylate, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, and the like.

  Preferably, 2,4-di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate and 2-t-butyl-6- (3- t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate.

  As said acrylate compound, it can select from a commercially available thing suitably and can be used. For example, Sumitizer GM (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., which is 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2,4 -Sumitizer GS (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., which is di-t-amyl-6- [1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate Can do. In particular, it is preferable to use a Sumilizer GS (registered trademark).

Although the compounding quantity of the said acrylate antioxidant in this invention is not limited, The range of 100-1000 ppm is preferable with respect to the above-mentioned all polypropylene resin composition. 200 to 800 ppm is more preferable, and 300 to 700 ppm is more preferable. When it exceeds 1000 ppm, the contamination of the cooling roll increases in the film forming step, which is not preferable. The film is also unfavorable because it dyes a pale yellow color unique to antioxidants. On the contrary, if it is less than 100 ppm, the combined effect described later is decreased, which is not preferable. It is preferable to lower the upper limit of the blending amount of the acrylate antioxidant alone than the above two kinds of antioxidants. The acrylate antioxidant is a polypropylene resin rubber compared to other antioxidants. Due to the high solubility in the component, it is more distributed to the rubber component in the film, and the rubber component portion has a slower crystallization rate by the cooling roll than the base resin, so that the rubber is in contact with the cooling roll. It is surmised that the above-mentioned acrylate antioxidant distributed to the components easily migrates to the cooling roll, and thus is caused by increasing the contamination degree of the cooling roll.
For example, this is a unique phenomenon that occurs in the present invention that does not occur in the film formation using the homopolypropylene resin disclosed in Patent Document 23 and the like described above.

  Specific examples of the phosphorus antioxidant include a heat stabilizer containing a trivalent phosphorus atom in the molecule, and the phosphorus atom has at least one P—O—C bond. For example, tributyl phosphite, trioctyl phosphite, trilauryl phosphite, tristearyl phosphite, tridecyl phosphite, tricresyl phosphite, tricyclohexyl phosphite, triphenyl phosphite, trilauryl thiophosphite, tris ( 2-ethylhexyl) phosphite, tris (isodecyl) phosphite, tris (tridecyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, tris (butoxyethyl) phosphite, tris (nonylphenyl) Phosphite, tris (3,5-di-t-butyl-4-hydroxyphenyl) phosphite, tris [4,4′-isopropylidenebis (2-t-butylphenol)] phosphite, tris (1,3- Gieste (Royloxyisopropyl) phosphite, 2-ethylhexyl diphenyl phosphite, decyl diphenyl phosphite, phenyl di-2-ethylhexyl phosphite, phenyl didecyl phosphite, phenyl diisodecyl phosphite, phenyl di (tridecyl) phosphite, diphenyl nonyl phosphite, Diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, diphenyl mono (tridecyl) phosphite, dibutyl hydrogen phosphite, 4,4′-isopropylidene diphenol alkyl (C12 to C15) phosphite, 4,4′-butylidenebis ( 3-methyl-6-tert-butylphenyl) di-tridecyl phosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl Sufite, 2,2'-ethylidenebis (4,6-di-t-butylphenol) fluorophosphite, bis (2,4-di-t-butyl-6-methylphenyl) .ethyl phosphite, 4,4 ' -Isopropylidenebis (2-t-butylphenol) di (nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite, diphenylpentaerythritol diphosphite, phenyl 4, 4'-isopropylidenediphenol pentaerythritol diphosphite, bis (4,6-di-t-butylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) Pentaerythritol diphosphite, phenyl -Bisphenol A pentaerythritol diphosphite, tetraphenyldipropylene glycol diphosphite, tetra (tridecyl) -1,1,3-tris (2-methyl-5-tert-butyl-4-hydroxyphenyl) butanediphos Phyto, tetra (C12-C15 mixed alkyl) -4,4'-isopropylidene diphenyl diphosphite, tetra (tridecyl) -4,4'-butylidenebis (3-methyl-6-t-butylphenol) diphosphite, tetrakis (4 , 6-Di-t-butylphenyl) -4,4′-biphenylene diphosphonite, tetrakis (2-methyl-4,6-di-t-butylphenyl) -4,4′-biphenylene diphosphonite Bis (octylphenyl) -bis [4,4′-butylidenebis (3-methyl) 6-t-butylphenol)] • 1,6-hexanediol diphosphite, hydrogenated-4,4′-isopropylidene diphenol polyphosphite, 9,10-di-hydro-9-oxa-9-oxa- 10-phosphaphenanthrene-10-oxide, 2-[{2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo (D, F) (1,3,2) -dioxaphos Fephin-6-yl} oxy] -N, N-bis [2-[{2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo (D, F) (1,3,2) -Dioxaphosphine-6-yl} oxy] ethyl] ethanamine, 1,1,3-tris (2-methyl-4-di-tridecylphosphite-5-t-butylphenyl) butane, 3,4 , 5,6-Tetraben Like 1,2-oxa phosphane-2-oxide.

  Preferably, those having no pentaerythritol skeleton, tris (2,4-di-t-butylphenyl) phosphite, tris (3,5-di-t-butyl-4-hydroxyphenyl) phosphite, Bis (2,4-di-t-butyl-6-methylphenyl) .ethyl phosphite, tetrakis (2-methyl-4,6-di-t-butylphenyl) -4,4'-biphenylenediphosphonite It is.

  Commercially available products can also be used as the phosphorus-based antioxidant used in the present invention. For example, Irgafos 168 (manufactured by Ciba Specialty Chemicals), Irgafos 38 (manufactured by Ciba Specialty Chemicals), GSY- P101 (manufactured by Yoshitomi Fine Chemicals), Ultranox 641 (manufactured by GE Specialty Chemicals), and the like.

  Although the compounding quantity of the said phosphorus antioxidant in this invention is not limited, The range of 500-5000 ppm is preferable with respect to the above-mentioned all polypropylene resin composition. 1000 to 4000 ppm is more preferable, and 1500 to 3000 ppm is more preferable. If it is less than 500 ppm, the effect of using an antioxidant described later decreases, which is not preferable. On the other hand, if it exceeds 5000 ppm, the effect of using an antioxidant described later is saturated, causing film whitening due to the migration of the antioxidant to the film surface, contamination of the cooling roll in the film forming process, and the like. It is not preferable.

  The phenolic antioxidant used in the present invention is an antioxidant having a phenol derivative in the molecule, such as 2,6-di-t-butyl-4-methylphenol, 2,6-di-t. -Butyl-4-ethylphenol, 2,6-dicyclohexyl-4-methylphenol, 2,6-di-t-amyl-4-methylphenol, 2,6-di-t-octyl-4-n-propylphenol 2,6-dicyclohexyl-4-n-octylphenol, 2-isopropyl-4-methyl-6-t-butylphenol, 2-t-butyl-2-ethyl-6-t-octylphenol, 2-isobutyl-4-ethyl -6-t-hexylphenol, 2-cyclohexyl-4-n-butyl-6-isopropylphenol, dl-α-tocopherol, t-butyl Droquinone, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6) -T-butylphenol), 2,2-thiobis (4-methyl-6-t-butylphenol), 4,4'-methylenebis (2,6-di-t-butylphenol), 2,2'-methylenebis [6- (1-methylcyclohexyl) -p-cresol], 2,2′-ethylidenebis (4,6-di-t-butylphenol), 2,2′-butylidenebis (2-t-butyl-4-methylphenol), 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5 -Di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, triethylene Glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxy) Phenyl) propionate], 2,2-thiodiethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-t -Butyl-4-hydroxy-hydrocinnamide), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, tris (2,6-dimethyl) 3-hydroxy-4-t-butylbenzyl) isocyanurate, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, tris [(3,5-di-t-butyl-4-hydroxy Phenyl) propionyloxyethyl] isocyanurate, tris (4-t-butyl-2,6-dimethyl-3-hydroxybenzyl) isocyanurate, 2,4-bis (n-octylthio) -6- (4-hydroxy-3) , 5-Di-t-butylanilino) -1,3,5-triazine, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, 2,2′-methylenebis (4-Methyl-6-tert-butylphenol) terephthalate, 1,3,5-trimethyl-2,4,6-tris (3,5-di- t-butyl-4-hydroxybenzyl) benzene, 3,9-bis [1,1-dimethyl-2- {β- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl]- 2,4,8,10-tetraoxaspiro [5,5] undecane, 2,2-bis [4- (2- (3,5-di-tert-butyl-4-hydroxyhydrocinnamoyloxy)) ethoxy Phenyl] propane, β- (3,5-di-t-butyl-4-hydroxyphenyl) propionic acid stearyl ester, and the like.

  Preferably, β- (3,5-di-t-butyl-4-hydroxyphenyl) propionic acid stearyl ester, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] Methane, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4- Hydroxybenzyl) benzene, dl-α-tocopherol, tris (2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate, tris [(3,5-di-tert-butyl-4-hydroxyphenyl) ) Propionyloxyethyl] isocyanurate, 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methyl) Butylphenyl) propionyloxy} ethyl] -2,4,8,10-tetra-oxa-spiro [5,5] undecane.

  Commercially available products may be used as the phenolic antioxidant used in the present invention, for example, Irganox 1010 (Ciba Specialty Chemicals), Irganox 1076 (Ciba Specialty Chemicals), Irganox 1330 (manufactured by Ciba Specialty Chemicals), Irganox 3114 (manufactured by Ciba Specialty Chemicals), Irganox 1425WL (manufactured by Ciba Specialty Chemicals) and the like.

  Although the compounding quantity of the said phenolic antioxidant in this invention is not limited, The range of 500-5000 ppm is preferable with respect to the above-mentioned all polypropylene resin composition. 1000 to 4000 ppm is more preferable, and 1500 to 3000 ppm is more preferable. If it is less than 500 ppm, the effect of using an antioxidant described later decreases, which is not preferable. On the other hand, if it exceeds 5000 ppm, the effect of using an antioxidant described later is saturated, causing film whitening due to the migration of the antioxidant to the film surface, contamination of the cooling roll in the film forming process, and the like. It is not preferable.

  Phenol-based antioxidants and phosphorus-based antioxidants have little selectivity for the antioxidant effect with respect to each component of the raw material resin composition described above, but acrylate-based antioxidants are used with the rubber part of the polypropylene-based block copolymer. It is known that the affinity is strong and the tendency to preferentially suppress the deterioration of the rubber part. On the other hand, regarding the generation of fish eyes, the contribution of the deterioration of the rubber part is large. Therefore, it is presumed that the combined use of the above-mentioned plurality of antioxidants led to a significant reduction in fish eyes.

  The method for preparing the polypropylene resin composition containing the antioxidant and the crystal nucleating agent used in the present invention is not particularly limited, and examples thereof include known methods. Examples thereof include a method of heat-melt kneading using a kneader such as a kneader, a Banbury mixer, or a roll, and a method of heat-melt kneading using a single screw or twin screw extruder. Various resin pellets may be dry blended. In the method for preparing the composition, the antioxidant and the crystal nucleating agent may be added directly to the respective powders, or may be added as a master batch previously mixed with the polypropylene resin. When adding as a masterbatch, it may be prepared for each additive or may be prepared by mixing two or more. Moreover, you may implement combining the commercially available resin in which the said additive was mix | blended well. In addition, the composition may be prepared in advance to be supplied to a film forming process and supplied to a film forming extruder, or the components constituting the composition may be supplied to the film forming extruder. It may be supplied and prepared to form a film.

The feature of the method for producing the surface-protective polypropylene resin film of the present invention is as follows:
Control of crystallinity in cooling condition control of molten resin Draft ratio control during take-up and cooling solidification of molten resin.

[Control of crystallinity in cooling condition control]
The extruded film of the present invention is an unstretched film formed by a T-die method, and the thickness of the film is not particularly limited, but is generally 1 to 500 μm, and a film having a preferred thickness is necessary. Selected.
Film forming conditions for using the polypropylene resin composition of the present invention as an extruded film are preferably performed at a die temperature of 200 ° C to 250 ° C and a cooling roll temperature of 40 to 65 ° C. 45-60 degreeC is more preferable. If the cooling roll temperature is less than 40 ° C., a crystallinity sufficient for heat-resistant dimensional stability cannot be obtained, which is not preferable. Conversely, when the temperature exceeds 65 ° C., a touch roll mark of the cooling roll is generated, which is not preferable, and the transparency may be extremely lowered. Moreover, although it does not specifically limit about cooling time, The range for 0.5 second or more is preferable. If the cooling time is less than 0.5 seconds, the cooling effect is insufficient, and a touch roll mark of the cooling roll is generated, which is not preferable. On the other hand, the upper limit of the cooling time is not particularly limited from the viewpoint of the degree of crystallinity of the film, but is preferably 5 seconds or less and more preferably 3 seconds or less from the viewpoint of economy and productivity.
When a crystal nucleating agent is used in combination as a means for arbitrarily adjusting the degree of crystallinity, it is necessary to add 100 ppm or less because there is a concern about an increase in fish eye of the film as described above. Therefore, the inventors found the control of the crystallinity by controlling the cooling conditions of the molten resin according to the cooling conditions.

[Draft ratio control]
In the extruded film of the present invention, the birefringence of the film can reach a predetermined range by adjusting the draft ratio in the drawing step after melt extrusion to a range of 0.4 to 3.0. It is generally known that the draft ratio is calculated according to the following film forming conditions.
Draft ratio = (film take-up speed / die exit melt resin speed) / air gap The air gap means the distance (cm) from the die exit to the take-up (cooling) roll contacting the melt resin.
When the draft ratio is less than 0.4, the thickness unevenness of the film increases, and the flatness of the film is deteriorated during the adhesive processing, which is not preferable. On the other hand, when the draft ratio exceeds 3.0, the birefringence exceeds the predetermined range, the impact resistance is remarkably lowered, and the mechanical properties of the film itself are deteriorated.
The conventional unstretched polypropylene film tends to increase the film take-up speed (by reducing the draft ratio) for the purpose of improving the heat-resistant dimensional stability. Controlling the degree of conversion, controlling the draft ratio at the time of film formation and taking-up of film to a certain range, and keeping the amount of 20 ° C xylene soluble part within a certain range, heat resistance dimensional stability and film flatness, It has been possible to provide a surface-protective polypropylene-based resin film that has a good balance of impact resistance and is difficult to deform in the adhesive coating process.

  The extruded film of the present invention can be subjected to surface treatment such as corona discharge treatment or flame treatment by a method generally employed industrially.

  In the present invention, it is important that the surface protective film is a surface protective film in which an adhesive layer is provided on at least one surface of the above-described surface protective polypropylene-based resin film. By the correspondence, the characteristics of the polypropylene resin film of the present invention described above can be effectively utilized, and the applicability in a wide field as a protective film is improved. In particular, for example, applications that prevent scratches, adhesion of dirt, contamination, etc. during the processing and assembly of electronic and precision products such as liquid crystal panels and polarizing plates, precision products, parts and related members, and connection of flexible printed circuit boards As a method of partially plating the terminal part, etc., a mask is formed by sticking an adhesive film to the non-plated part and then plating, or a resist film or etching resistance provided on the non-etched surface in the etching process when manufacturing the shadow mask Use in plating and etching processes such as methods for protecting the film, methods for protecting the surface of the semiconductor element by laminating a film on the surface without the circuit of the semiconductor element, and simplifying the process when assembling the semiconductor device, etc. Protection of various precision products and parts that are particularly demanding to suppress contamination and defects, and addition of such products and parts It can be suitably used as a protective film in and assembly process. Further, the polypropylene resin film of the present invention is excellent in heat-resistant dimensional stability, and in the above-mentioned adhesive processing, for example, even if the drying temperature in the drying process is increased, the occurrence of hot stagnation and film sagging is suppressed. It becomes possible to increase the productivity of adhesive processing. Moreover, generation | occurrence | production suppression of the inferior goods resulting from a hot bath or film sagging can be suppressed.

  The kind, thickness, adhesive strength, and the like of the pressure-sensitive adhesive layer are not limited. What is necessary is just to select suitably by market demand. Moreover, the lamination method of this adhesive layer is not limited. Any of the coating method and the extrusion laminating method may be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, but may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all included in the technical scope of the present invention.

  The measurement and evaluation methods employed in this specification are as follows.

1. Melt flow rate [MFR]
According to JIS K7210, the method of Condition-14 (load 2.16 kg, temperature 230 ° C.
Measured with

2. Ethylene content Measured by ¹³ C-NMR method by the method described on page 616 of Polymer Handbook (1995, published by Kinokuniya Shoten)

3. Haze Based on JIS-K-6714, it was measured using “Haze Tester J” manufactured by Toyo Seiki Seisakusho.

4). Film crystallinity Measured using wide-angle essence line diffraction transmission method (RIGAKU RINT2500).

5. Birefringence (△ n)
Using an Abbe refractometer, the refractive index Nx in the film flow direction and the refractive index Ny in the film flow direction and the orthogonal direction were measured and calculated using the following formula.
△ n = │Nx-Ny│

6). Thickness fluctuation rate One film sample having a width of 1 m was measured at a pitch of 3 cm in the width direction, and the average thickness was calculated. Next, either the maximum value or the minimum value among the measured film samples was calculated by the following calculation formula using either one having a large difference from the average thickness.
Thickness variation rate (%) = | (average thickness) − (maximum value or minimum value) | / (average thickness) × 100

7). Blocking resistance In accordance with ATM-D1893-67, a load of 90N was applied to the area of A4 size and left for 2 hours in an atmosphere of 60 ° C. After removing the load, the peeling resistance with a φ5 aluminum rod was measured at a moving speed of 100 mm / min. It measured on condition of this.

8). Young's modulus In accordance with JIS K7127, sample shape conforming to No. 1 type test piece (sample length 200 mm, sample width 15 mm, distance between chucks 100 mm), MD direction under conditions of crosshead speed 500 mm / min It measured at 23 degreeC about (film longitudinal direction).

9. Impact strength In accordance with ASTM D3420, the sample is cut to 55 to 60 cm in the vertical direction and 9 to 10 cm in the horizontal direction. Read the strength value when punched using an impact tester in a 23 ° C room to the first decimal place. The operation is repeated 10 times, and the average value is obtained.

10, Fisheye 33.3cm in the flow direction × 30cm in the direction transverse to the flow direction, placed on a plate irradiated with a fluorescent lamp from under the film, visually observed with transmitted light, Measure fish eyes of 0.1 mm or more. Next, if the counted fish eye is immersed in liquid nitrogen and hardened, it is cut in half with a razor and the cross section of the fish eye is observed with a microscope at 50 to 300 times. For example, if there is no foreign matter such as cellulose, it is an unmelted lump, a lump due to gelation of a part of the raw material, or a gel-induced fish such as lump due to partial deterioration of the material during molding. Judged as eye. If there is a nucleus, it is judged as a fish eye caused by a foreign object and excluded from the count.

11. Ratio of xylene soluble part at 20 ° C. (%)
After 5 g of the sample was completely melted in 500 ml of boiling xylene, the temperature was lowered to 20 ° C. and left for 4 hours or more. Thereafter, the precipitate and the solution were separated by filtration, and the filtrate was dried and dried at 70 ° C. under reduced pressure. From the mass of the obtained dried product, the 20 ° C. xylene-soluble part amount was measured, and the ratio was determined.

12 Intrinsic viscosity ([η], unit: dl / g)
Using a Ubbelohde viscometer, reduced viscosities were measured at three concentrations of 0.1, 0.2 and 0.5 g / dl. The intrinsic viscosity is calculated by the calculation method described in “Polymer Solution, Polymer Experiments 11” (published by Kyoritsu Shuppan Co., Ltd.), page 491. That is, the reduced viscosity is plotted against the concentration and the concentration is extrapolated to zero Obtained by extrapolation. Polypropylene was evaluated at a temperature of 135 ° C. using tetralin as a solvent.
Intrinsic viscosity of 20 ° C xylene soluble part: [η] EP
The intrinsic viscosity of the insoluble portion at 20 ° C .: [η] P and the total intrinsic viscosity: [η] T were measured, respectively, and the weight ratio with respect to the whole of the 20 ° C. xylene soluble portion: X was calculated from the following formula. Asked.
[Η] EP = [η] T / X− (1 / X−1) [η] P

13. Heat deformation resistance The molded film was cut into 5 cm in the flow direction and 25 cm in the direction transverse to the flow direction, and the film pieces were horizontally placed in a 120 ° C. dry heat oven with both ends held by a metal frame. Heat-treated for minutes. Immediately after the heat treatment, the film was taken out from the oven and allowed to cool at room temperature for 30 minutes, and then the sag (elongation) state due to the weight of the film itself was visually observed in the following range.
○: No dripping or almost no dripping.
(Triangle | delta): A drooping state is observed slightly.
X: A hanging state is observed.

14 Processability The occurrence of wrinkles and tarmi was visually observed when the molded film was rolled up into a roll with a width of 1300 mm using a slitter (SXR-140 type, manufactured by Toshin Co., Ltd.).
○: Wrinkles and tarmi are not generated during running and winding.
Δ: Slight wrinkles and tarmi were observed during running or winding.
X: Wrinkles and tarmi were clearly observed during running or winding.

15. Elastic film deformation rate The formed film was cut at 10 mm in the flow direction and 3 mm in the direction transverse to the flow direction, and 110 mm at a load rate of 5 g and a heating rate of 10 ° C./min using a thermal analyzer TMA-60 manufactured by Shimadzu Corporation. The temperature was raised to 120 ° C., then raised to 120 ° C. over 10 minutes, and then the dimensional change [%] after cooling to 30 ° C. was determined.
The product obtained by multiplying this value by the Young's modulus was defined as the elastic film deformation rate.
A: Elastic film deformation rate is less than 6.0 × 10 3 ◯: Elastic film deformation rate is 7.0 × 10 3 to 7.0 × 10 3 Δ: Elastic film deformation is 7. 0 × 10 3 to less than 8.0 × 10 3 ×: Elastic film deformation rate is 8.0 × 10 3 or more

Example 1
69 parts by weight of homopolypropylene resin (MFR = 7), 22 parts by weight of block copolymerized polypropylene resin (MFR = 2) having a rubber component amount of 13.0% and an ethylene content of 6.5%, manufactured by Mitsui Chemicals, Inc. An acrylate antioxidant comprising a homopolypropylene resin (MFR = 7) containing 7 parts by weight of an elastomer (trade name: TAFMER P0480) and 5% by weight of Sumizer GS (manufactured by Sumitomo Chemical Co., Ltd.) which is an acrylate antioxidant. 2 parts by weight of the masterbatch resin containing is melt-extruded with a T-die film forming machine so that the resin temperature becomes 250 ° C., the cooling roll temperature is 60 ° C., and the cooling time is 2.0 seconds (film forming speed 60 m / min). Draft ratio at the time of taking up the resin 1.56 (die slip gap: 0.5 mm, die slip outlet molten resin speed: 4.8 m / min, air gap : To obtain an unstretched film having a thickness of 40μm at the deposition conditions of 8 cm). The resin temperatures in the supply zone, kneading zone and metering zone of the extruder were set to 230, 240 and 235 ° C, respectively. The results are shown in Table 1.
The polypropylene-based resin film obtained in this example was good in all properties shown in Table 1 and high in quality.

(Example 2)
0.15% by mass of Irgafos 168 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phosphorous antioxidant and 0 of Irganox 1010 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phenolic antioxidant Random copolymerization of block copolymer polypropylene resin (MFR = 2) with an ethylene content of 3.0% and an ethylene content of 3.0% with an ethylene content of 13.0% and an ethylene content of 6.5% A polypropylene resin film of Example 2 was obtained in the same manner as in Example 1 except that 5 parts by weight of polypropylene resin (MFR = 7) was added and the cooling roll temperature was 45 ° C. The results are shown in Table 1.
The polypropylene-based resin film obtained in this example was good in all properties shown in Table 1 and high in quality.

(Example 3)
0.15% by mass of Irgafos 168 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phosphorous antioxidant and 0 of Irganox 1010 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phenolic antioxidant Mixing 86 parts by weight of homopolypropylene resin (MFR = 7) containing 15% by mass and 14 parts by weight of elastomer (trade name: Toughmer P0480) manufactured by Mitsui Chemicals, cooling roll temperature of 50 ° C., drawing of molten resin Example 3 was carried out in the same manner as in Example 1 except that the draft ratio was 2.50 (die slip gap: 0.8 mm, die slip outlet molten resin speed: 3.0 m / min, air gap: 8 cm). A polypropylene resin film was obtained. The results are shown in Table 1.
The polypropylene resin film obtained in this example had the same properties as the polypropylene resin film obtained in Example 1 and was of high quality.

(Comparative Example 1)
30 parts by weight of a random copolymer polypropylene resin (MFR = 7) having an ethylene content of 0.5% by mass, and 0.22 mass of Irgafos 168 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phosphorus-based antioxidant % Of the rubber component containing 0.28% by mass of Irganox 1010 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phenolic antioxidant and 8.5% ethylene content and 5.0% ethylene content A polypropylene resin film of Comparative Example 1 was obtained in the same manner as in Example 1 except that 70 parts by weight of block copolymerized polypropylene resin (MFR = 2) was blended. The results are shown in Table 1.
The polypropylene-based resin film obtained in this comparative example has a large elastic film deformation rate, and easily undergoes plastic deformation during adhesive processing.

(Comparative Example 2)
0.15% by mass of Irgafos 168 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phosphorous antioxidant and 0 of Irganox 1010 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a phenolic antioxidant 92 parts by weight of block copolymerized polypropylene resin (MFR = 2) having a rubber component content of 13.0% and an ethylene content of 6.5%, an elastomer (trade name: Mitsui Chemicals) A polypropylene resin film of Comparative Example 2 was obtained in the same manner as in Example 1 except that 20 parts by weight of Tuffmer P0480) was blended and the cooling roll temperature was 60 ° C. The polypropylene resin film obtained in this comparative example is inferior in heat deformation resistance.

(Comparative Example 3)
In the method of Example 2, the polypropylene resin film of Comparative Example 3 was obtained in the same manner as in Example 2 except that the cooling roll temperature was changed to 20 ° C. The results are shown in Table 2.
Although the polypropylene resin film obtained in this comparative example has good transparency, the crystallinity of the film is lowered, resulting in poor quality such as poor heat-resistant dimensional stability and poor processability.

(Comparative Example 4)
In the method of Example 2, the polypropylene resin film of Comparative Example 4 was obtained in the same manner as in Example 2 except that the cooling roll temperature was changed to 80 ° C. The results are shown in Table 2.
The polypropylene-based resin film obtained in this comparative example was of low quality such that transparency and impact strength were lowered due to extreme crystallization, and the processing suitability was inferior. Further, due to heat loss during film formation, touch roll marks are generated, the flatness of the film itself is impaired, or the film quality is deteriorated.

(Comparative Example 5)
In the method of Example 2, instead of the random copolymer polypropylene resin (MFR = 7), bis (2,2′-methylene-bis (4,6-di-tert-butylphenyl) is used as the cyclic organophosphate compound. Phosphate) -aluminum hydroxide salt (Asahi Denka Kogyo Co., Ltd., ADK STAB NA-21) 1 wt% of a homopolypropylene resin (MFR = 7) containing a crystal nucleating agent containing 5 parts by weight of a masterbatch resin In addition, a polypropylene resin film of Comparative Example 5 was obtained in the same manner as in Example 2 except that the cooling roll temperature was 30 ° C. The results are shown in Table 2.
The polypropylene resin film obtained in this comparative example had a low quality because the fish eye increased significantly compared to the polypropylene resin film obtained in Example 2.

(Comparative Example 6)
In the method of Example 2, the draft ratio at the time of taking the molten resin is changed to 0.25 (die slip gap: 2.0 mm, die slip outlet molten resin speed: 1.2 m / min, air gap: 8 cm). Except for the above, a polypropylene resin film of Comparative Example 6 was obtained in the same manner as in Example 2. The results are shown in Table 2.
The polypropylene-based resin film obtained in this comparative example has a low quality because the thickness variation rate is deteriorated, the flatness of the film is lowered, and the birefringence is smaller than the lower limit, so that the heat resistant dimensional stability and workability are inferior. there were.

  The results are shown in Tables 1 and 2.

The present invention is excellent in heat-resistant dimensional stability and flatness, excellent in impact resistance and bonding processability, and is suitable as a base film for a protective film, for example.
Since the polypropylene resin film for surface protection of the present invention is excellent in heat-resistant dimensional stability, for example, it is suitable for secondary processing such as adhesive processing, and is particularly subjected to treatment such as drying at a high temperature around 130 ° C. In addition, since the occurrence of hot stagnation and film sagging is suppressed, the productivity of the secondary processing can be improved, and the generation of defective products due to hot sag and film sagging can be suppressed.
Further, the present invention has small thickness spots.
Moreover, it is preferable that the polypropylene resin film of the present invention does not substantially contain an antiblocking agent. For example, when a film containing an antiblocking agent is run, the antiblocking agent falls off due to wear or the like. Therefore, the contamination and the occurrence of troubles due to the fallout are suppressed.
In addition, although the present invention does not substantially contain a lubricant or an anti-blocking agent, the surface roughness is appropriate, the slipperiness and blocking resistance of the film are good, and the film is excellent in rigidity. Is easy to handle.
In addition, since the polypropylene resin film for surface protection of the present invention does not substantially contain a lubricant or an anti-blocking agent, when used as a base film of a protective film, a lubricant or Since there is no migration of the anti-blocking agent, contamination of these objects to be packaged and protected objects is suppressed.
Moreover, since it is excellent in transparency, it is excellent in the visibility of a to-be packaged object or a to-be-protected body.
In addition, because of the strength of the film, it is excellent in handleability.
In addition, despite its improved heat-resistant dimensional stability, it has excellent impact strength and maintains good impact resistance by being made of block polypropylene resin. High reliability when there is.

Claims (8)

A polypropylene-based resin film composed mainly of polypropylene resin, a 20 ° C. xylene solubles content of less than 16% greater than 9%, the content of the crystal nucleating agent is at 100ppm or less, and, A polypropylene resin film for surface protection, wherein the film has a crystallinity of 34 to 65% and a birefringence (Δn) of 0.4 × 10 ^{−3 to} 2.5 × 10 ⁻³ . 2. The polypropylene resin film for surface protection according to claim 1, wherein the thickness variation rate of the film is 1 to 10%.   The surface-protective polypropylene resin film according to claim 1, wherein the content of the antiblocking agent in the film is 50 ppm or less and the blocking resistance is 10 mN or less.   The polypropylene resin film for surface protection according to claim 1, wherein the content of the lubricant in the film is 50 ppm or less. Wherein said Fi Tsu Shuai maximum diameter is more than 0.2mm in the film is 0 or / 1000 cm ^2, and Fi Tsu Shuai of maximum diameter of less than 0.2mm is 100/1000 cm ² or less The polypropylene resin film for surface protection according to claim 1.   The surface-protective polypropylene-based resin film according to claim 1, wherein the film has a longitudinal Young's modulus at 23 ° C. of 500 Mpa or more.   The polypropylene resin film for surface protection according to claim 1, wherein the impact strength of the film at 23 ° C. is 0.3 J or more.   A surface protective film comprising a pressure-sensitive adhesive layer on at least one surface of the surface-protective polypropylene-based resin film according to claim 1.