JPS645541B2 - - Google Patents

Description

[Detailed description of the invention]

[] BACKGROUND TECHNICAL FIELD OF THE INVENTION The present invention relates to a tracing film in which a chemical coat layer is provided on the surface of a polyolefin film base layer. As an alternative to tracing paper made of natural pulp paper that has been used for many years,
A tracing film was proposed in which a polyester film was used as a base material, and a chemical coat layer made of a roughening material (e.g., calcium carbonate, silica, etc.) and a binder (e.g., unsaturated polyester resin) was provided on the surface of the film. −13543
No. 49-37585), it is partially used due to its advantages such as strength and dimensional stability. On the other hand, it is also known to use a polyolefin film as a base material, and since polyolefin film is relatively inexpensive, its development is expected. However, since the polyolefin film has poor adhesion to the chemical coat layer, it has the disadvantage that the coat layer peels off when writing with a pencil. Furthermore, since polyolefin film is flexible, if you write with a hard pencil (for example, one with a hardness of H to 4H), high pressure will create a dent in the writing area, which can be erased with an eraser. When rewriting, this rewriting is difficult. In order to prevent peeling between the chemical coat layer and the polyolefin film base layer, the composition for forming the chemical coat layer is a chlorinated polypropylene emulsion, a water-soluble polymer adhesive, and glyoxal and silica powder as waterproofing agents. (Special Publication No. 49-37428)
(see publication). A tracing film obtained by applying this composition to a polypropylene film can be written on with a pencil and the coating layer will not peel off. However, the tracing film obtained in this way is also plagued with the above-mentioned problem of the dents inherent in the base polyolefin film. [] Summary of the Invention The present invention aims to provide a solution to the above-mentioned problems, and uses a tracing film having a chemical coat layer formed by dispersing a specific hard inorganic fine powder in a specific crosslinked resin matrix. The goal is to achieve this goal. Therefore, the tracing film according to the present invention is characterized in that it consists of the following layers A and B. A: A base material layer consisting of a single layer of a polyolefin film having a filler content of 35 to 60% by weight or a laminate having the same on the surface. B A chemical coat layer made of the following cured products (a) to (c) provided on the surface of this polyolefin film layer. (a) Polymer of hydroxyl group-containing acrylic or methacrylic acid ester having a hydroxyl value of 20 to 200 (b) Polyisocyanate (c) Inorganic fine powder having a Mohs hardness of 4 or more. However, (a) and (b) are present in a ratio such that the ratio of isocyanate equivalent ([NCO]) to hydroxyl group equivalent ([OH]) is [NCO]/[OH] from 0.5 to 3.0. . Furthermore, (c) is present in an amount of 40 to 230 parts by weight per 100 parts by weight of (a)+(b). Effects According to the tracing film of the present invention, the following effects can be obtained. (1) The chemical coat layer does not peel off even when written with a hard pencil, and the characters are written even with low writing pressure.
Symbols, frames, etc. can be clearly identified (chemical coat layer has good adhesion and writability). (2) Characters written with a pencil can be easily erased with an eraser (erasable with an eraser). (3) It is possible to write again with a pencil on the part erased with an eraser (re-writability). (4) This tracing film has moderate translucency, making it easy to identify entries.
Furthermore, the drafted drafting paper can be diazo-copied in a short time. The opacity of the tracing film of the present invention is controlled by the translucency of the base layer, and is hardly affected by the chemical coat layer. Even if cellophane tape or the like is attached to the surface, the opacity hardly decreases, and therefore the identification of entries and the diazo reproduction characteristics do not change either. Further, even if the chemical coat layer peels off, the translucency as a tracing film is substantially maintained, and since the base layer itself functions as synthetic paper, writability is also maintained. This (1) improvement in adhesion is due to the anchoring effect of the filler protruding on the surface of the polyolefin film to the chemical coat layer, and the fact that a part of the polyisocyanate used to form the chemical coat layer acts as an anchor coating agent. It is understood that it was expressed by In addition, the improvements in writability, eraser erasability, and rewritability in (1) to (3) are due to the toughness of the crosslinked polymer formed from (a) and (b) and the inorganic fine particles dispersed therein. This is thought to have occurred because the powder has a high degree of hardening, making it possible to write clearly even with low writing pressure, and the fine inorganic powder on the surface does not fall off even when rubbed by an eraser. . As mentioned above, the tracing film based on a polyolefin film is difficult to rewrite, so the tracing film of the present invention based on a polyolefin film can have the rewriting properties. This effect can be said to be unexpected. Finally, it is understood that the appropriate opacity in (4) was achieved because the base film contained an appropriate amount of filler. [] Detailed Description of the Invention The tracing film of the present invention consists of a base layer A and a chemical coat layer B provided on the surface thereof. 1 Base Material Layer A (1) Structure The base material layer consists of a single layer of a polyolefin film having a filler content of 35 to 60% by weight or a laminate having the same on the surface. A preferred base material layer is one made of a laminate. A more preferred base material layer is one in which each layer is stretched biaxially or uniaxially, or a combination thereof. The most preferred base layer is one in which the surface layer (i.e. high filler content layer) and optionally some of the layers in contact with its lower surface are uniaxially oriented, and further some of the layers in contact with its lower surface are biaxially oriented; It is. Since tracing films are usually written on one side, the high filler content surface layer may be present on only one side of the laminate. The stretching ratio is 2.5 to 10 times for each axis, preferably 3
~8 times, which is normal. When the base layer is composed of a single layer with a high filler content, this layer is preferably biaxially stretched from the viewpoint of tear resistance. The surface of the stretched high filler content layer will have an anchoring effect on the chemical coat layer with the filler particles protruding. Furthermore, as a result of stretching, fine cracks are occasionally generated within the layer or on the layer surface. The surface of the surface layer on which the chemical coat layer is to be provided is preferably one that has been subjected to corona discharge treatment, oxidation treatment, or other surface treatment for polyolefin films in order to further enhance the adhesion of the chemical coat layer. . From the viewpoint of ease of treatment, corona discharge treatment is preferable. (2) Material Another requirement for the base layer for the tracing film of the present invention is that the layer in contact with the chemical coat layer is a polyolefin film with a filler content of 35 to 60% by weight. "Polyolefin" in the case of polyolefin-based film refers to homopolymers of ethylene, propylene, butene-1, hexene-1, 4-methyl-pentene-1, other _C2 to _C10 α-olefins, and copolymers of these It includes both polymers and copolymers of these and other copolymerizable monomers (for example, (meth)acrylic acid esters, vinyl acetate, vinyl chloride, etc.). In order to have the properties necessary as a tracing film,
It is desirable that the "polyolefin" be not excessively rubbery, preferably resinous. These may be used in combination. The filler to be dispersed in such polyolefins can be any known or usable filler for polyolefins. Specific examples include calcined clay, calcium carbonate, silica, alumina, barium sulfate, titanium oxide, clay, and others. Preferred among these are silica, titanium oxide, clay, and calcium carbonate. These may be used in combination. The blending amount of such a filler is 35 to 60% by weight (based on the weight after blending). If the filler content is less than 35%, the adhesion between the base layer and the chemical coat layer is poor, the dimensional stability of the base layer and, by extension, the product film is poor, and the product film has low incineration properties. Filler amount is 60% by weight
If it exceeds this value, the opacity will become too high and it will be difficult to provide the film with the translucency required for tracing paper. Also, such high filler content films are difficult to form. The preferred filler content is 40-50% by weight. When the base material layer is a laminate, the layers other than the high filler content surface layer are subject to the following criteria: the type of resin used, the presence or absence of a filler and its type, the number of such layers, and the presence or absence of stretching. It can be any purposeful thing. A preferred layer is a polyolefin film of the same kind or different kind as the surface layer, and is substantially free of fillers. (3) Production Methods for producing monolayers of filler-containing polyolefin films and laminates having the same as the surface are already well known. Such a manufacturing method, for example,
-40794, Japanese Patent Publication No. 49-1782, and the specification of US Pat. No. 3,154,461. However, although the methods described in these documents are suitable for obtaining highly opaque synthetic paper, they do not disclose a method for producing a translucent film suitable for tracing paper. In order to obtain a translucent film suitable for tracing paper, stretching should be carried out so that substantially no voids are formed in the film as described in GB 1,096,064. Specifically, when polypropylene is used as a film material, the stretching temperature is slightly lower than the melting point of polypropylene, and the stretching speed is 15 to 100 m/min vertically and 8 to 20 m/min horizontally.
Stretch 3 to 10 times in minutes. In the most preferred embodiment, a polypropylene film for the center layer having a melt index of 0.5 to 3 g/10 minutes is stretched in advance in the longitudinal direction by 3 to 7 times at a temperature of 150 to 163°C, and at least one side of the film for the center layer is Then, polypropylene containing 35 to 60% by weight of inorganic fine powder and having a melt index of 2 to 10 g/10 minutes and higher than that of the film for the center layer is melt-laminated, and then the obtained laminated film is laminated. At a temperature of 160 to 164°C in the transverse direction and higher than the longitudinal stretching temperature.
It consists of stretching the film 3.5 to 10 times and then annealing the laminated film at a temperature of 165 to 168°C for 6 to 45 seconds. 2 Chemical Coat Layer B The chemical coat layer consists of an acrylic or methacrylic acid (hereinafter referred to as (meth)acrylic acid) ester polymer matrix crosslinked by urethane bonds and hard fine inorganic powder dispersed therein. be. (1) (Meth)acrylic acid ester polymer (a) This polymer is a homopolymer or copolymer of (meth)acrylic acid ester having at least one (preferably one) hydroxyl group in the alcohol moiety of the ester. It is a combination. This hydroxyl group-containing polymer has a hydroxyl value of 20~
200, preferably 60-130. Here, the hydroxyl value is a value expressed in mg of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups when 1 g of a sample is acetylated. The (meth)acrylic acid ester giving such a polymer is a monoester of an alcohol compound having at least two (preferably two) hydroxyl groups. In addition to typical alkanols, "alcohol compounds" here include
It also includes polyoxyalkylene glycol (alkylene is about _C2 to _C3 ).
Specific examples of such (meth)acrylic esters include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, di- or polyethylene glycol mono(meth)acrylate, di- or polypropylene glycol mono( meth) acrylate, glycerin mono(meth)
There are acrylates and others. This (meta)
The acrylic acid polymer can be, and is preferred, a copolymer of the monomers instead of a homopolymer as described above. There are various types of monomers that can be copolymerized with the above-mentioned (meth)acrylic esters, and any suitable monomer can be used. Specific examples include methyl to cyclohexyl (meth)acrylate, styrene, vinyltoluene, and vinyl acetate. The hydroxyl group-containing (meth)acrylic acid ester component of the copolymer is 10
~50% by weight, especially 15-30% by weight, is preferred. Note that this hydroxyl group-containing (meth)acrylic ester polymer is produced by processing a polymer having a group that can be converted into a hydroxyl group, instead of producing it by polymerizing a hydroxyl group-containing (meth)acrylic ester as described above. It can also be produced by making it have a hydroxyl group. Polymerization is conveniently carried out by solution polymerization. (2) Polyisocyanate (b) Specific examples include 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, and these. There are compounds having two or more isocyanate groups in the molecule obtained from derivatives. (3) Hard inorganic fine powder (c) Examples of the inorganic fine powder having a Mohs hardness of 4 or more include fine quartz powder, fine glass powder, and fine calcined alumina powder. Among these, quartz powder, which tends to protrude onto the surface of the chemical coat layer, is preferable in terms of writability and less increase in the opacity of the chemical coat layer. If the Mohs hardness is less than 4, the hardness of the chemical coat layer is too low to withstand friction caused by an eraser, and the writability is also poor. These inorganic fine powders have an average particle size of 0.1~
Preferably it is 5 microns, especially 0.5 to 3 microns. If the average particle size is larger than 5 microns, the surface will feel rough when writing, and even if the writing looks dark, the pencil lead will suffer from strong friction and the paper will be easily stained. On the other hand, if the average particle size is less than 0.1 micron, writing with a pencil is poor. (4) Quantitative ratios The quantitative ratios of components (a) to (c) are as follows. First, in (a) and (b), the equivalent ratio of hydroxyl group to isocyanate group [NCO]/[OH] is 0.5.
The quantitative ratio is determined to be in the range of ~3.0. If the polyisocyanate content is small and the ratio is less than 0.5, the adhesion between the chemical coat layer and the base layer will be insufficient, and the toughness of the chemical coat layer will also decrease, resulting in poor rewriting properties. On the other hand, if there is too much polyisocyanate and the ratio exceeds 3.0, unreacted isocyanate groups tend to remain, resulting in a problem of stickiness of the chemical coat layer. If we focus only on the reactivity with the hydroxyl group-containing (meth)acrylic acid polymer, theoretically this ratio is 1, but if we consider the improvement of adhesion to the surface of the base material layer, this ratio is greater than 1. be, especially 1.1
It is preferable that it is about 1.5. (c) is 40 to 230 parts by weight per 100 parts by weight of (a) + (b)
Parts by weight, especially 60 to 100 parts by weight, are preferred.
If the hard inorganic fine powder is too small, writability and rewriting properties will be reduced, and if it is too large, the chemical coat layer will become brittle and adhesive properties will also be reduced. (5) Curing The curing reaction occurs when the hydroxyl group in (a) and the isocyanate group in (b) come into contact, but curing due to contact between both groups is achieved by providing a layer of the composition that provides a chemical coat layer on the base material. It is normal to do this later (details later). 3 Formation of chemical coat layer The chemical coat layer is a layer of the composition consisting of (a) to (c) provided on the base material layer, and a reaction between the hydroxyl group of (a) and the isocyanate group of (b) progresses. It can be formed by forming a hardened layer. The application of a layer of the composition consisting of (a) to (c) on a substrate is preferably carried out by applying the composition in liquid form, in particular in solution form, onto the substrate. be able to. The solution of the compositions (a) to (c) to be applied usually has a solid content concentration of about 10 to 50% by weight. The solvent used can generally be an inert organic solvent that dissolves (a) and (b). When a hydroxyl group-containing (meth)acrylic acid ester polymer is obtained by solution polymerization, it is convenient to prepare a coating solution by adding (c) to the solution and adjusting the concentration. Generally, solvents that may be used include acetic acid esters, toluene, xylene, methyl ethyl ketone, and others. Application of such a solution can be performed by a known method such as a gravure roll method, a kiss roll method, a reverse roll method, a doctor knife method, or a bar method. The coating amount is 1 to 10 g/based on solid matter after drying.
About ^m2 is appropriate. After coating, evaporate the solvent used and store at room temperature to 100℃.
If the coated film is kept at a temperature of
The crosslinking reaction with (b) progresses to complete the chemical coat layer. 4 Product Tracing Film The tracing film of the present invention has an opacity (JIS-P-8138) of 10 to 60%, preferably 25 to 45%, from the viewpoint of distinguishability of written items and diazo copying characteristics. It is customary to manufacture it as follows. Further, the hardness of the cured resin forming the chemical coat layer is usually manufactured to have a pencil hardness of 2H or more. If the hardness of the chemical coat layer is lower than 2H, the writability and rewritability will be insufficient. 5 Experimental example (1) Production of base film Polypropylene “Mitsubishi Noblen MA-6” manufactured by Mitsubishi Yuka Co., Ltd. (trade name, melting point = 164°C) 87
High-density polyethylene "Yukalon Hard EY-40" manufactured by Mitsubishi Yuka Co., Ltd. (trade name, melting point = 130℃)
After melt-kneading a composition consisting of 10 parts and 3 parts of fired clay using an extruder,
It was extruded into a sheet at a temperature of 250°C, and the sheet was cooled to a temperature of about 50°C. Next, this sheet was heated to about 153° C. and then stretched four times in the longitudinal direction using the difference in peripheral speed between the roll groups to obtain a uniaxially stretched film. Separately, polypropylene "Mitsubishi Noblen MA-3" manufactured by Mitsubishi Yuka Co., Ltd. (trade name, melting point = 163
℃) and 43 parts of calcined clay were melt-kneaded using two other extruders,
Each sheet was extruded from two dies at a temperature of 250°C and laminated on the uniaxially stretched film to obtain a three-layer sheet. This three-layer sheet was once cooled to 60°C, then reheated to a temperature of approximately 163°C, stretched 8 times in the transverse direction using a tenter, and then
After passing through an oven set at 165°C to set the heat, the film was cooled to about 60°C, and the edges were slit to make the biaxially stretched base layer film of the middle layer 30 microns thick and the front and back layers uniaxially stretched. Composite stretched films each having a wall thickness of 15 microns were obtained. The overall opacity of this three-layer film is 32%.
It was hot. (2) Tracing film production Examples 1 to 3, Comparative Examples 1 and 2 15 parts of 2-hydroxyethyl methacrylate, 50 parts of methyl methacrylate, 35 parts of ethyl acrylate
and 100 parts of toluene were charged into a three-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, and after purging with nitrogen, the mixture was heated at 80°C for 4 hours using 0.6 part of 2,2'-azobisisobutyronitrile as an initiator. Polymerized. The obtained solution was a 50% toluene solution of a hydroxyl group-containing methacrylic acid ester polymer having a hydroxyl value of 65. Next is "Coronate HL" 75%
Ethyl acetate solution (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene isocyanate type), Mohs hardness 7
Fine quartz powder with an average particle size of 1.1 microns was blended in the solid content ratio shown in Table 1, and the solid content was 40% with butyl acetate.
After adjusting the composition, it was coated on the surface of the polypropylene stretched film obtained in the above example at a dry solid content of 3 g/m ² , and then cured at 80° C. for 1 hour to obtain a tracing film. Table 1 shows the opacity and suitability for drawing paper of the obtained tracing film. Comparative Examples 3 and 4 Calcium carbonate with a Mohs hardness of 3 and an average particle size of 0.8 and diatomaceous earth with a Mohs hardness of 1 to 1.5 and an average particle size of 2.0 were used instead of the fine quartz powder of Example 2, and applied and hardened in the same manner. A tracing film was obtained. Table 1 shows the opacity and suitability for drawing paper of the obtained tracing film. (3) Measurement of physical properties (1) Tape removability Adhesive tape is attached to the coating side and peeled off rapidly.Removal status: 〇 = Not peeled off × = Peeled off. (2) Writability Measured using a writability tester manufactured by Toyo Seiki. That is, place the tracing film on the table and insert the pencil lead (3H,
A load of 142 g was applied to the pencil lead (lead diameter: 0.3 mm), and then the pencil lead was slid 10 cm onto the stretched film, and the density of the line drawn was measured using a Grayscale Photographic Step Table No. 2 manufactured by Kodak. Good writability = 15 or higher Practical = 12-14 Impractical = 11 or lower (3) Erasability When the written characters are erased with an eraser,
Good (〇) if the characters can be erased and no writing marks remain on the stretched film.
If the characters could be erased but traces of writing remained, they were rated as acceptable for practical use (△). (4) Re-writability After rubbing the surface of the tracing film with an eraser 10 times, the above-mentioned writability test was conducted.

[Table] *2 Comparative example of hardness of cured resin products formed from (a) and (b) 5 A commercially available thermoplastic high molecular weight polyester (hydroxyl value 7) was used instead of the polyacrylic polyol used in the example. , this was combined with "Coronate HL" and fine quartz powder with an average particle size of 1.1μ in terms of solid content.
They were mixed at a ratio of 96:4:80 ([NCO]/[OH] = 1.3, the hardness of the resin excluding quartz powder is H), and a coating liquid with a solid content of 30% was prepared using methyl ethyl ketone as a solvent. This coating solution was applied to the surface of the polypropylene composite stretched film obtained in the above example at a dry solid content of 3.
After coating at a concentration of g/m ² , the coating was cured at 80° C. for 1 hour to obtain a tracing film. The opacity of the obtained film was 33%, but the coating surface peeled off easily in the tape removability test, and the erasability with an eraser was also poor, making it unsuitable as a tracing film.

Claims (1)

[Claims] 1. A tracing film comprising layers A and B as shown below. A: A base material layer consisting of a single layer of a polyolefin film having a filler content of 35 to 60% by weight or a laminate having the same on the surface. B A chemical coat layer made of the following cured products (a) to (c) provided on the surface of this polyolefin film layer. (a) Polymer of hydroxyl group-containing acrylic or methacrylic acid ester having a hydroxyl value of 20 to 200 (b) Polyisocyanate (c) Inorganic fine powder having a Mohs hardness of 4 or more. However, (a) and (b) are present in such a ratio that the ratio of isocyanate equivalent ([NCO]) to hydroxyl group equivalent ([OH]) is 0.5 to 3.0. do. Furthermore, (c) is present in an amount of 40 to 230 parts by weight per 100 parts by weight of (a)+(b).