JPH0637573B2 - Method for producing void-containing stretched molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a method for producing a void-containing stretched molded product. More specifically, the present invention relates to a method for producing a void-containing stretched molded article containing crystalline polypropylene as a main component and having excellent surface uniformity.

[Prior Art] A cavity-containing stretched molded product is used as a uniaxially or biaxially stretched film for general packaging materials, decorative materials, synthetic papers, calligraphic printing papers, etc. by utilizing its characteristics such as opacity and pearly luster. It is also widely used as a tape, ribbon or filament for packaging materials, woven yarns and the like.

Conventionally, for example, the following method has been proposed as a method for producing a void-containing stretched molded product.

(a) a method of forming a large number of bubbles by adding a foaming agent during molding, (b) a method of stretching a composition containing a large amount of an inorganic filler to form voids (Japanese Patent Publication No. Sho 62-24532 and JPA
63-117043, etc.), (c) a method of dispersing high melting point polymers such as nylon and polyester in crystalline polypropylene (JP-A-61-157547 and US Pat. No. 4,377,6)
However, these methods have the following drawbacks. That is, in (a), it is necessary to make a complicated selection of the foaming agent depending on the application of molding conditions. Air bubbles tend to become coarse, resulting in a decrease in gloss. A thin film such as a film has a drawback that uniform fine foaming is difficult.

In the case of (b), deterioration of fluidity during extrusion, clogging of a screen pack of an extruder, moisture absorption / coarse foaming due to an inorganic filler, and poor dispersion are likely to occur. The productivity is extremely poor in that it takes a long time to replace the resin when the resin is changed. Further, the obtained product has a low gloss, and only a dull product can be obtained, and in addition, it is inferior in impact resistance and tensile strength.

In (c), nylon, saturated polyester, etc. are poor in compatibility with crystalline polypropylene, and the melting temperature,
Since the flow behavior (solution viscosity) and the like are very different from those of crystalline polypropylene, it is difficult to uniformly disperse both. As a result, the prepared original fabric is likely to be non-uniform, breakage occurs during stretching, and stable productivity is poor. The obtained stretched product is also made opaque, but the problem remains that the void content is still low and only a dull tone with low gloss can be obtained.

[Problems to be Solved by the Invention] As a result of various investigations by the present inventors to overcome these drawbacks of the conventional method and obtain an opaque and highly glossy void-containing stretched molded product, crystalline polypropylene has a specific petroleum resin content. It has been found that an improved void-containing stretched molded product can be obtained by stretching a composition in which a specific amount having a specific high softening point is added. However, even with this method,
As a result of the addition of the high softening point petroleum resin, when the melt-extruded composition is rapidly cooled, it tends to be difficult for the composition to adhere to the quenching roll. On the other hand, in the case of stretching using a heating roll, on the contrary, the low molecular weight component of the petroleum resin may be deposited on the roll surface, or the stretched sheet may not be uniformly peeled from the roll. As a result, there are drawbacks that workability is deteriorated and that the stretched product contains voids uniformly inside, but uneven glossiness is likely to occur on the surface. In particular, the higher the softening point and the larger the amount added, the more the surface unevenness is remarkably generated.

The present inventors have examined the method of eliminating the surface unevenness of the high addition type stretch molded product with this high softening point petroleum resin, and added a specific high softening point petroleum resin and a specific surfactant to crystalline polypropylene. The present invention was completed by finding that the roll adhesion and the peelability from a heating roll can be significantly improved by using the composition described above, and the surface gloss can be significantly improved without impairing the properties of the void-containing stretched molded product. did.

Means for Solving the Problems That is, the present invention relates to the following production method: (1) Softening point (ring and ball method) 160 to 230 in a cyclopentadiene-based petroleum resin with respect to crystalline polypropylene ℃
5 to 50% by weight and nonionic surfactant 0.05 to
A composition containing 3% by weight is melt-extruded at a temperature higher than the softening point of the petroleum resin by 10 ° C. or more, and the composition is melted at a temperature not higher than the crystalline melting point of the crystalline polypropylene in at least one direction.
A method for producing a void-containing stretched molded article, which comprises stretching at least twice.

As the crystalline polypropylene used in the present invention, a crystalline homopolymer of propylene, a copolymer of ethylene or more of propylene as a main component or one or more other α-olefins having 4 or more carbon atoms or a binary copolymer or 70% by weight of the mixture insoluble in boiling n-heptane
The above content is preferably 80% by weight or more.
Specifically, for example, crystalline polypropylene, crystalline ethylene / propylene copolymer containing 70% by weight or more of propylene component, crystalline propylene / 1-butene copolymer, crystalline propylene / 1-hexene copolymer, etc. And a propylene-based copolymer having a crystalline melting point such as the crystalline ethylene / propylene / 1-butene copolymer.

This crystalline polypropylene has a melting index (hereinafter referred to as "MFR") of 0.1 to 20 measured by JIS K7210-1976.
g / 10 min, preferably 0.3 to 10 g / min, and having a crystal melting point (hereinafter referred to as “Tm”) measured by a scanning differential calorimeter (abbreviation DSC) method of 110 ° C. or higher, preferably It is of 125 ° C.

Examples of the cyclopentadiene-based petroleum resin used in the present invention include the following: cyclopentadiene obtained from steam cracking of petroleum naphtha, etc., dicyclopentadiene, alkyl substituted products thereof and oligomers thereof, and mixtures thereof. In a petroleum resin (HR) obtained by polymerizing a fraction containing at least one selected (hereinafter referred to as “cyclopentadiene component”) as a main component, a cyclopentadiene-based component is contained in an amount of 50% by weight or more, And its softening point (ring and ball method)
Of 160 to 230 ° C., preferably 170 to 220 ° C., having a high molecular weight and a high softening point (HSHR); and 50 parts of the above petroleum resin (HR) containing cyclopentadiene-based components.
A conventionally known method containing a content of not less than wt%, that is,
150 to 3 in the presence of a solvent, using a catalyst such as a metal such as palladium, nickel or cobalt or an oxide thereof.
Softening point (ring and ball method) 160 to 230 obtained by hydrogenation under the conditions of a temperature of 00 ° C. and a hydrogen pressure of 10 to 150 kgf / cm ^2.
Hydrogenated cyclopentadiene-based resin (HGHR) or a mixture thereof at 0 ° C, preferably 170 to 220 ° C.

When the softening point of the resin is 155 ° C. or lower, it is not suitable for obtaining the opaque void-containing stretched molded product which is the object of the present invention. The reason is that a stretched film of a film made of a polypropylene-based composition to which a known hydrogenated petroleum resin is added becomes transparent (JP-A-60-90734 and JP-A-60-2).
(See Japanese Patent No. 10647). Further, the production cost of the petroleum resin having a softening point of 240 ° C. or higher becomes extremely high, and the dispersibility in polypropylene is also poor, so that the gloss of the product is significantly lowered, which is not preferable.

The polymerization for producing the high softening point petroleum resin used in the present invention can be carried out by a generally known method. For example, under an atmosphere of an inert gas such as nitrogen gas in the presence or absence of a solvent, preferably at a temperature of 220 ° C. or higher, and under a pressure capable of holding the polymerization system in a liquid phase for several hours or more, for example, It can be obtained by thermal polymerization, but in order to produce a high softening point petroleum resin, a reaction at a high temperature and for a long time is required as compared with conventionally known petroleum resins. Therefore, in addition to one-step polymerization, multi-step polymerization of two or more steps is also preferable. Further, hydrogenation of the petroleum resin is also carried out at a high temperature for a long time,
Highly hydrogenated ones are desirable because they have excellent compatibility with polypropylene. The polymerization process and the hydrogenation process can be performed either continuously or batchwise.

The cyclopentadiene-based petroleum resin thus obtained has an iodine value of 20 at a softening point (ring and ball method) of 170 to 220 ° C.
The following hydrogenated cyclopentadiene petroleum resins are most preferred. The resin has the following advantages: Especially excellent compatibility with polypropylene The composition can be stably processed Molded products contain fine and uniform cavities, and thus have excellent opacity and surface gloss. It can be processed into stretched molded products.

Examples of the nonionic surfactant used in the present invention include the following: Known nonionic surfactants such as higher aliphatic amines, higher fatty acid amides or ethylene oxide adducts such as higher alkylphenols.

General formula (i) (Here, R is an alkyl group having 12 to 22 carbon atoms, R ¹ and
R ² is H or a fatty acid-forming acyl group having 12 to 22 carbon atoms. An ethylene oxide adduct of N, N-dialkanol higher aliphatic amine represented by n and m represented by 1 to 6) or a derivative thereof is preferable.

General formula (ii) (Here, R is an alkyl group having 12 to 22 carbon atoms, R ¹ and
R ² is H or a fatty acid-forming acyl group having 12 to 22 carbon atoms. N and m are numbers of 1 to 6), N, N-dialkanol higher aliphatic amides or derivatives thereof are preferable. Specific examples of N, N-dialkano higher aliphatic amines (hereinafter, "N, N-" may be omitted)
Can include one or more higher alkylamines such as palmityldiethanolamine, stearyldiethanolamine, oleyldiethanolamine, behenyldiethanolamine, and erucyldiethanolamine. Of these, preferred is one containing palmityldiethanolamine or stearyldiethanolamine as a main component.

Specific examples of the N, N-dialkanol higher fatty acid amide (hereinafter, “N, N-dialkanol” is omitted) include palmitoylamide (commonly known as “palmitylamide”) and stearoylamide (commonly known as “stearylamide”). , Oleoylamide, behenoylamide, elcoylamide and the like. Among these, preferred are those containing palmitoylamide or stearoylamide as a main component.

Higher fatty acid esters of polyhydric alcohols, higher aliphatic alcohols, etc .: In particular, esters of polyhydric alcohols having 3 to 5 valences and higher fatty acids having 12 to 22 carbon atoms: Among them, glycerol (also known as "glycerin") higher fatty acid ester, sorbitol (Also known as “sorbitan”) Higher fatty acid esters and the like and ethylene oxide adducts thereof are preferred.

Specific examples include glycerol monostearate, pentaerythritol monostearate, sorbitol monostearate, glycerol monobehenate, pentaerythritol monobehenate, sorbitol monobeheate, glycerol distearate, glycerol tristearate and the like. You can Particularly preferred is glycerol monostearate.

The composition used in the present invention contains crystalline polypropylene with 5 to 50% by weight of a cyclopentadiene-based petroleum resin having a softening point (ring and ball method) of 160 to 230 ° C. and 0.05 to 3% by weight of a nonionic surfactant. It is the composition. If the addition amount of the high softening point petroleum resin is 3% by weight or less, the effect of providing opacity due to the formation of cavities, which is the object of the present invention, is insufficient.
When the content is more than 10% by weight, extrusion unevenness and stretch breakage during molding are likely to occur and, in addition, the productivity is extremely reduced, which is not preferable. The amount of nonionic surfactant added is 0.03% by weight.
If the amount is less than 4.5%, the effect of improving the surface gloss is not seen, and if it is more than 4.5% by weight, the surface becomes rough due to moisture-absorption foaming and stretch breakage occurs, which is not preferable.

The composition used in the present invention can be made into a product by appropriately adjusting the addition range of each component within the scope of the present invention depending on the thickness of the molded product, the draw ratio, the target opacity, the surface gloss and the like. .

In the above composition used in the present invention, additives known to be added to polypropylene as necessary, for example, known phenol-based, phosphorus-based or thioether-based antioxidants / processing stabilizers, stearin Acids, higher fatty acids such as calcium stearate and metal salts thereof, lubricants / slip agents such as fatty acid amides, calcium carbonate, tanks, inorganic fillers such as silica, organic and inorganic pigments, various polymers, etc. You may mix | blend suitably in the range which does not exist.

As a method for producing this composition, a method of mixing the respective components with an ordinary blender or a mixer can be adopted. It is desirable to use each component as a pelletized composition after melt mixing using an extruder, a Banbury mixer or the like. In particular, the higher the softening point of the high softening point petroleum resin, the more important it is to knead and disperse the composition. In order to obtain this composition, for example, the high softening point petroleum resin powder and a nonionic surfactant (and an antioxidant and other predetermined additives) are added to crystalline polypropylene powder, and the powder form is sufficient. After mixing, melt kneading is performed at a temperature exceeding the crystalline melting point of the crystalline polypropylene. Desirably, the composition is pelletized by melt-kneading with an extruder or the like at a temperature higher than the softening point of the highly softened petroleum resin, and particularly preferably at a temperature higher than the softening point of the petroleum resin by 20 ° C. or more, followed by cooling and cutting. It is a method of doing things.

A masterbatch obtained by adding a large amount of the petroleum resin to polypropylene or another polymer is used, and further mixed with polypropylene and / or a nonionic surfactant to be used as a final composition. The scheme is also useful.

From the composition thus obtained, for example, an unstretched raw fabric is prepared by a melt extrusion method using an apparatus composed of an extruder and a die, and then uniaxially or biaxially stretched under specific conditions to obtain the composition of the present invention. A target void-containing stretched molded product is obtained.

In this method, an unstretched original fabric is formed as follows: To form a flat material such as a film sheet and a slit tape, a band, etc., an extruder and a T die or a circular die are used. 10 ° C or higher, preferably 20 ° C or higher than the softening point of the petroleum resin blended in the raw material composition.
Melt-kneading is performed at a high temperature as described above, molten resin is extruded from a die, cooled and solidified. If the melting temperature for obtaining the unstretched original fabric by this operation is significantly lower than the above lower limit of temperature, the desired effect of improving the surface gloss is insufficient. Further, it is desirable that the molten resin is cooled by a mirror surface roll contact or a rapid cooling by introducing into water, and the temperature of the roll or the refrigerant is 10 to 10.
It is around 0 ° C. A particularly desirable cooling method is 30 to 90 ° C.
Using a mirror roll or two mirror rolls kept at
It is a method of cooling at least one side of the film or cooling both sides of the film while nipping with a pair of rolls. This method is particularly effective for the present invention because a raw material having a very good surface smoothness can be obtained and, as a result, a void-containing molded article having a very good surface gloss even after stretching can be obtained.

The stretching of the present invention is a known uniaxial stretching method such as roll stretching, oven stretching, hot plate stretching or tubular stretching, a known stretching method such as simultaneous or sequential biaxial stretching such as a combination of roll stretching and tenter stretching. Although it can be carried out by any method, it is necessary that the stretching temperature is not higher than the crystalline melting point of the crystalline polypropylene in the composition.

In the present invention, the actual temperature at which the crystalline polypropylene can be oriented substantially by stretching is called the stretching temperature, and this temperature is preferably in the range of substantially 80 to 160 ° C.

The draw ratio for obtaining the stretch-formed product of the present invention needs to be 2 times or more in one direction, and is preferably 4 times or more in the case of biaxial stretching. In order to form many cavities that are substantially opaque,
In the case of uniaxial stretching, it may be 4 times or more, and in the case of biaxial stretching, either simultaneous biaxial stretching or sequential biaxial stretching may be used, but the stretching ratio is preferably 20 to 60 times in area ratio.

In the unstretched molded product obtained by molding the composition used in the present invention, voids do not occur, and it is a transparent or translucent molded product, and its density is larger than that of polypropylene alone. Lightweight, opaque void-containing moldings aimed at by the invention cannot be obtained.

Further, the stretch-molded product of the present invention, like a normal stretch-molded product, may be heat-treated after stretching under tension or while being relaxed by several% as necessary, or subjected to corona discharge treatment in an atmosphere of air, oxygen, nitrogen or the like. Alternatively, surface treatment such as plasma treatment can be applied.

According to the production method of the present invention, extremely high productivity can be realized as compared with the conventionally known method, and the obtained stretch-molded product has a large number of fine voids therein, and the total ray thereof is usually An opaque and lightweight molded product having a transmittance of 50% or less and a density of 0.8 g / cm ³ or less can be obtained.

Examples and Comparative Examples Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The characteristic values used in the following examples and comparative examples were evaluated by the following methods.

Softening point (° C; ring and ball method): Compliant with JIS K 2207 Iodine value: Compliant with JIS K0070-1966 g of iodine added to unsaturated components in 100 g of sample
Number MFR (g / 10min): Conforms to JIS K7210-1976 test condition 14 (230 ° C, 2.16kgf) Measured for crystalline polypropylene resin Crystal melting point (Tm; ° C): Scanning working calorimeter (abbreviation: D)
SC), set about 10 mg of sample, measure from room temperature at a temperature rising rate of 20 ° C./min, measure the endothermic curve associated with melting of the crystal, and determine the temperature at which the peak associated with melting is located as Tm. did. When a plurality of melting peaks are observed, the temperature at which the peak having the largest area is located is Tm.

Apparent density (g / cm ³ ): Measured weight per 1 m ^{2 of the} molded product, converted to 1 cm ² and divided by thickness (cm) Total light transmittance (%): JIS K- According to 6714 Gloss (%): According to ASTM D523 (measurement angle 20 degrees) Example 1 Crystalline polypropylene (Tm 163 ° C, MFR 1.5g / 10m)
in, boiled n-heptane insoluble content 96%) 100 parts by weight of powder, 0.2 parts by weight of phenolic antioxidant BHT, 0.3 parts by weight of calcium stearate and hydrogenated cyclopentadiene-based petroleum resin [softening point (ring and ball method ) 177
C., iodine value 12] 22 parts by weight and 1 part by weight of monostearyl ester of stearyldiethanolamine were added and mixed with a Henschel mixer, and then the composition was passed through an extruder having a co-rotating twin screw 25
The mixture was melt-kneaded at 0 ° C., extruded, cooled and cut to obtain a pelletized composition. Next, the obtained composition was melt-extruded at a temperature of 250 ° C. using a 30 cm T-die connected to an extruder having a diameter of 65 mm, and both sides were cooled with a pair of mirror surface cooling rolls kept at 30 ° C. An unstretched original sheet having a thickness of 1.0 mm was obtained. This raw sheet has an apparent density of 0.92g / cm
^{At 3} , it was smooth and translucent. Next, this raw sheet was cut into a square shape and stretched 5.2 times in the vertical direction of the original sheet at a temperature of 155 ° C. using a pantograph type biaxial stretching tester, and immediately in a direction (horizontal) to it. It was stretched 8.2 times, heat-treated at the same temperature while being relaxed by 3% in both directions, then air-cooled and taken out. This operation was performed for 10 original sheets to obtain 10 sequentially biaxially stretched films. The characteristic values of the film having a central portion of 15 cm × 15 cm of the 10 sheets were shown to be extremely opaque and have a pearly luster and were even as follows.

Apparent density (g / cm ³ ): 0.72 (10 sheets average) Thickness (μm): Average 44 (max 46, min 42) Total light transmission (%): Average 22 (max 25, min 20) Gloss (%) : Average 66 (maximum 69, minimum 62) The hydrogenated cyclopentadiene-based petroleum resin is generally known as a component containing 91% by weight of dicyclopentadiene component obtained by steam cracking of naphtha and the subsequent decomposition step. Polymerization was carried out by controlling the polymerization time, temperature and pressure by the method, and further hydrogenation was carried out in the presence of a nickel-based catalyst at 250 ° C. and hydrogen pressure of 80 kgf / cm ² .

Comparative Example 1 A composition was prepared in the same manner except that the monostearyl ester of stearyldiethanolamine was removed from the composition of Example 1. A raw sheet was prepared from the obtained composition in accordance with Example 1, and biaxially stretched successively using a pantograph type biaxial stretching tester under the same conditions, and 10 sheets were successively biaxially stretched. Obtained. 15cm x 1 in the center of these 10 films
The characteristic values of the 5 cm film are as follows, showing that the opacity is excellent, but the maximum and minimum are greatly separated, and the fluctuation (unevenness) of the glossiness is extremely large.

Apparent density (g / cm ³ ): 0.73 (10 sheets average) Thickness (μm): Average 45 (maximum 49, minimum 40) Total light transmittance (%): Average 23 (maximum 31, minimum 18) Gloss (% ): Average 44 (maximum 65, minimum 31) Comparative Example 2 Among the components of the composition used in Example 1, the hydrogenated cyclopentadiene-based resin was changed to one having a softening point of 145 ° C. and an iodine value of 11. A composition was prepared according to the same example, and the following steps were carried out in the same manner as in Example 1 to successively prepare a biaxially stretched film. The obtained film has an apparent density of 0.92 g / cm ³ ,
The film had almost no opacity (extremely transparent) with a total light transmittance of 95% and a glossiness of 138%.

Example 2 Crystalline ethylene / propylene / 1-butene terpolymer (ethylene content 4.5% by weight, 1-butene content 4.0
% By weight, Tm 130 ° C., MFR 4.6 g / min) 11 parts by weight, 0.2 parts by weight of phosphorus antioxidant [trade name: P-EPQ (manufactured by ADEKA ARGUS CORPORATION)], zinc stearate
0.2 parts by weight, titanium oxide 1.0 parts by weight, hydrogenated cyclopentadiene-based petroleum resin [softening point (ring and ball method) 175 ° C., weight average molecular weight (GPC method) 1385, iodine value 13] 20 parts by weight and nonionic surfactant As a mixture, 0.2% by weight of stearyldiethanolamine and 0.5% by weight of glycerin monostearate were mixed, and a pelletized composition was obtained in the same manner as in Example 1.

Next, this composition was supplied to a uniaxially stretched film / sheet manufacturing apparatus comprising a combination of an extruder having a diameter of 65 mm, a T die and a heating roll type stretching apparatus, melt-extruded at 230 ° C., and then on a mirror-cooled roll at 20 ° C. It was rapidly cooled to obtain a stretched raw fabric sheet having a thickness of 1.0 mm and an apparent density of 0.92 g / cm ³ . After heating this sheet to 95 ° C. using a heating roll group, 10
After stretching 5.5 times in the vertical direction (film formation) between two sets of nip rolls kept at 0 ℃, heat-treat at 3% relaxation at the same temperature, and cool with a cooling roll at 30 ℃ to wind the film. A uniaxially stretched sheet of about 0.23 mm was obtained.

This uniaxially stretched sheet has a density of 0.73 g / cm ³ and a total light transmittance of 9
% And glossiness 57%, there was no surface unevenness, and it was opaque and had a pearly luster.

The above hydrogenated cyclopentadiene-based petroleum resin contains 76% by weight of a dicyclopentadiene component obtained by polymerizing components obtained by steam cracking of naphtha and a subsequent decomposition step, and an aromatic hydrocarbon fraction. 21
It was a hydride of a petroleum resin containing wt%.

Example 3 Crystalline polypropylene (Tm 163 ° C., MFR 3.0 g / 10 m
in, boiling n-heptane insoluble content 95%) to 100 parts by weight of powder, 0.2 parts by weight of phenolic antioxidant BHT, phosphorus antioxidant [trade name: P-EPQ (manufactured by ADEKA ARGUS CORPORATION) )] 0.1 parts by weight, calcium stearate 0.1 parts by weight, ground calcium carbonate (average particle size 0.8 μm)
5 parts by weight, 0.8 parts by weight of a nonionic surfactant (4 mol adduct of oleylamine with ethylene oxide) and hydrogenated cis-lopentadiene-based petroleum resin [softening point (ring and ball method) 177
C., iodine value 12] 15 parts by weight were mixed, and a pelletized composition was obtained in the same manner as in Example 1.

This composition was melt-extruded at an extrusion temperature of 250 ° C. and rapidly cooled by a mirror-like cooling roll at 40 ° C. to obtain an unstretched raw fabric sheet. This sheet was preheated with a heating roll group and then stretched 4.5 times in the vertical direction between two sets of nip rolls kept at 135 ° C., and then introduced into a tenter sequential biaxial stretching device.
It was stretched 9.0 times in the horizontal direction in an atmosphere of 2 ° C. Then about 4
The film was heat-treated in an atmosphere of 170 ° C. while being relaxed, air-cooled, and wound to obtain a biaxially stretched film.

The obtained biaxially stretched film is opaque and has a pearly luster, and its characteristic values are a thickness of 50 μm and an apparent density of 0.65 g /
It had a cm ³ , a total light transmittance of 12% and a glossiness of 52%, and showed a stability within a fluctuation range of each characteristic of ± 3% when measured at 30 points within a range of 100 m in the length direction.

As the hydrogenated cyclopentadiene-based petroleum resin, a hydrogenated petroleum resin containing 85% by weight of a dicyclopentadiene component was used.

Comparative Example 3 A pelletized composition was prepared in the same manner as in Example 1 except that a nonionic surfactant was removed from the composition of Example 3. A biaxially stretched film was sequentially prepared from the obtained composition according to Example 3. The obtained sequentially biaxially stretched film had a thickness of 50 μm, an apparent density of 0.64 g / cm ³ and a total light transmittance of 11%, and although the opaqueness was good, the glossiness was generally inferior, and the surface was streaky. Besides showing a lot of unevenness, the glossiness when measured at 30 points in the length direction of 100 m is 43% on average, 58% maximum, 17% minimum.
However, the fluctuation range was an extremely large value of ± 48%.

Example 4 Crystalline polypropylene (Tm 163 ° C., MFR 3.0 g / 10 m
in, boiling n-heptane insoluble content 95%) to 100 parts by weight of powder, 0.2 parts by weight of phenolic antioxidant BHT, phosphorus antioxidant [trade name: P-EPQ (manufactured by ADEKA ARGUS CORPORATION) )] 0.1 parts by weight, calcium stearate 0.1 parts by weight, ground calcium carbonate (average particle size 0.8 μm)
5 parts by weight, 0.8 part by weight of a nonionic surfactant (ethylene oxide 4 mol adduct of oleylamine) and hydrogenated cyclopentadiene-based petroleum resin [softening point (ring and ball method) 163
C., 25 parts by weight of iodine value 10] were mixed, and a pelletized composition was obtained in the same manner as in Example 1.

This composition was melt-extruded at an extrusion temperature of 230 ° C. and rapidly cooled with a mirror-like cooling roll at 40 ° C. to obtain an unstretched raw fabric sheet. After preheating this sheet with a heating roll group, it was stretched 5.0 times in the vertical direction between two sets of nip rolls kept at 125 ° C., and then introduced into a tenter method sequential biaxial stretching device.
It was stretched 9.6 times in the horizontal direction in an atmosphere of 0 ° C. Then about 4
The film was heat-treated in an atmosphere of 165 ° C. while being relaxed by%, air-cooled and wound to obtain a biaxially stretched film.

The obtained biaxially stretched film is opaque and has a pearly luster, and its characteristic values are a thickness of 50 μm and an apparent density of 0.80 g /
It had a cm ³ , a total light transmittance of 17%, and a gloss of 55%, and the fluctuation range of each property when measured at 30 points in the range of 100 m in the length direction showed stability within ± 1.4%.

[Effects of the Invention] The method of the present invention is extremely excellent in producing a void-containing stretched molded product as compared with a conventionally known method, and is also excellent in high opacity, lightweight and surface uniformity as a molded product. Can be provided. In addition, the obtained void-containing stretched molded product is used for general packaging materials, decorative materials,
It can be widely used for packaging materials, woven yarn, synthetic paper, etc.

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Claims (5)

[Claims] 1. A softening point (ring and ball method) 160-2 in a cyclopentadiene-based petroleum resin relative to crystalline polypropylene.
5 to 50% by weight of 30 ° C and nonionic surfactant
A composition containing 0.05 to 3% by weight is melt extruded at a temperature higher than the softening point of the petroleum resin by 10 ° C. or more, and stretched at least twice in at least one direction at a temperature not higher than the crystalline melting point of the crystalline polypropylene. A method for producing a void-containing stretched molded article, comprising: 2. A softening point (ring and ball) selected from cyclopentadiene-based petroleum resins selected from petroleum resins containing 50 wt% or more of cyclopentadiene-based components or hydrogenated cyclopentadiene-based petroleum resins obtained by hydrogenating the petroleum resins. Method) A method for producing a void-containing stretched molded article according to claim 1, wherein an iodine value of 20 or less at 170 to 220 ° C is used. 3. The nonionic surfactant is one or more selected from an ester consisting of a polyhydric alcohol having 3 to 5 valences and a higher fatty acid having 12 to 22 carbon atoms and a derivative thereof. Item 3. A method for producing a void-containing stretched molded article according to Item 1 or 2. 4. The cavity according to claim 1, wherein the nonionic surfactant contains as a main component one selected from the group represented by the following general formulas () and (). A method for producing a stretched and contained product. (i) (ii) (Here, R is an alkyl group having 12 to 22 carbon atoms, R ¹
And R ² is H or a fatty acid-forming acyl group having 12 to 22 carbon atoms. n and m are numbers 1 to 6). 5. An unstretched raw material is formed by rapidly cooling at least one surface of the melt-extruded composition with a mirror-like cooling roll kept at 30 to 90 ° C., and then having a temperature not higher than the crystalline melting point of the crystalline polypropylene. The method for producing a void-containing stretched molded article according to any one of claims 1 to 4, wherein the stretched molded article is stretched at least twice in one direction at a temperature.