JPS6034473B2 - pressure sensitive copy paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive copying paper, and more particularly to a pressure-sensitive copying paper having in a microcapsule coating layer fine particles having adhesive properties obtained by spray-drying an aqueous suspension or emulsion of a polymer. It concerns pressure copying paper.

In general, electron-donating organic coloring agents such as crystal violet lactone and benzylleucomethylene flue, and electron-accepting coloring agents such as activated clay, attapulgite, phenolic compounds, aromatic carboxylic acids or metal salts thereof, are used. Pressure-sensitive copying paper, which applies the principle of color development through reaction, is a paper coated with color-forming agent-containing microcapsules made by methods such as phase separation method, interfacial polymerization method, and JN-situ method, coated on one side of a supporting substrate ( CB), bottom paper (CF) in which a coloring agent is applied to one side of the supporting substrate, and inner paper (CFB) in which capsules and coloring agent are applied to different sides of the same substrate, which are used when making multiple copies. are used in combination as appropriate.

Also, it is in a form called a single coloring paper in which the capsule and the coloring agent are coated on the same side. One of the important properties required of such pressure-sensitive copying paper is that it is capable of producing clear, high-density colored images during copying, but it also has the ability to produce clear, high-density colored images during copying, while at the same time, One example is that it does not cause unnecessary colored stains. In order to satisfy these required characteristics, microcapsules must have practical mechanical strength such as pressure resistance, abrasion resistance, and impact resistance. Various difficulties arise in achieving the required characteristics. Until now, in order to improve the pressure resistance and abrasion resistance of such pressure-sensitive copying paper, particles slightly larger than the capsule particle diameter (hereinafter referred to as stilt material) have been used.
A means of dispersing the microcapsules in the coating layer was proposed.
As the stilt material, inorganic pigments, fine particles of natural polymeric substances, fine particles of synthetic polymeric substances made by methods such as suspension polymerization or mechanical crushing (US Pat. No. 3,625,736), microspheres (JP-A-Sho 48-32013), starch particles (Tsubaki Kosho No. 47-1178), etc., but each has its own drawbacks.

For example, when inorganic pigment fine particles are used as the stilt material, normally available powders have a wide particle size distribution, so it is necessary to use powders with a relatively small average particle size of around 1.5 times the capsule particle size. When used, it contains a considerable proportion of particles smaller than the capsule particle size, which is not effective in improving pressure resistance, so that only copy paper with low coloring ability can be obtained. When using this method, although it is effective in improving pressure resistance, only copy paper with very poor abrasion resistance is obtained. Furthermore, when microspheres are used as the stilt material, since they are hollow, they collapse under relatively weak pressure, and the expected effect of improving pressure resistance is not observed. In addition, when starch particles or polymer particles such as styrene, vinyl chloride, or pinyl acetate are used as the stilt material,
Since the adhesion of the fine particles themselves is weak, there is a lack of bonding force between the particles, between the particles and the surface of the supporting substrate, or between the particles and the microcapsules, resulting in a drawback that the abrasion resistance is rather poor.
In addition, for this reason, a method for improving friction resistance by combining starch particles with an adhesive (Japanese Patent Publication No. 48-3320
4) has also been proposed, but it is accompanied by a reduction in coloring ability due to the addition of an adhesive. The present invention aims to improve the above-mentioned drawbacks, and includes a water-soluble polymer in an aqueous emulsion or suspension of a synthetic polymer, and then spray-drying the resulting fine particles to coat microcapsules. It is characterized by being dispersed throughout the layer.

The thus obtained polymer fine particles of the present invention have a good particle size distribution, and since the fine particles themselves have strong adhesive properties, they can be bonded like conventional stilt materials. It is possible to strongly bond between the fine particles and the supporting substrate or between the fine particles and the capsules without using adhesive, and therefore it has become possible to improve the pressure resistance and abrasion resistance without reducing the coloring ability.

The polymers used for the purpose of the present invention are preferably polymers obtained by suspension polymerization or emulsion polymerization, such as acrylonitrile, methacryloetrile, methyl methacrylate, ethyl methacrylate, propyl methacrylate. , butyl methacrylate, amyl methacrylate, octyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, octyl acrylate,
Styrene, Q-methylstyrene, butadiene, isoprene, chloroprene, vinyl acetate, vinyl propionate,
Vinyl butyrate, ethyl vinyl ether, fluoride.

Examples include homopolymers or copolymers of propyl vinyl ether, butyl vinyl ether, ethylene, propylene, butene-1, isobutylene, vinyl chloride, vinylidene chloride, and the like. In addition, water-soluble polymers include cellulose,
Natural and synthetic polymers such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxyethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, casein, and gelatin can be mentioned. It is desirable to add such a water-soluble polymer in an amount of 1 to 1% by weight, more preferably 3 to 7% by weight, based on the weight of the polymer. The spray drying method itself can be any conventionally known method and does not require any special means.

In this case, according to a preferred embodiment, the emulsion or suspension of the polymer is spray-dried, and when the polymer particles are in the wet solid state, the viscosity, talc, silica,
By adding inert substances such as diatomaceous material, titanium dioxide, etc., stilt materials which are highly preferred for the purposes of the present invention can be obtained. It is desirable to add such an inert substance in an amount of about 3 to 2% by weight based on the weight of the polymer. In the present invention, the average particle size of the polymer stilt material is preferably 1.5 to 7 times, more preferably 2 to 5 times, the average particle size of the microcapsules.

In addition, the ratio of the stilt material dispersed in the capsule coating layer is 1/15 to 1/1 of the weight of the capsules in the coating layer.
It is desirable to use the ratio of In this case, of course, there is no preclude the use of conventionally used starch particles, cellulose powder, etc. in combination as long as the effects of the present invention are not significantly impaired. EXAMPLES Next, examples of the present invention will be shown to specifically explain the present invention, but the present invention is not limited to the following examples.

Note that unless otherwise specified, parts and % indicate parts by weight and % by weight, respectively. Example 1 100 parts of 6000 alkylnaphthalene containing 18 parts of crystal violet lactone and 7 parts of benzylleucomethylene blue were mixed with 58 parts of a 7% acid-treated gelatin aqueous solution.
The 0th floor is emulsified into the emulsion, and then 10% gum arabic aqueous solution 290 tate is added and mixed, and further 280 ml of water is added.
Floor B was added to maintain the system temperature at approximately 4000°C.

Next, a 10% acetic acid aqueous solution was added to adjust the pH of the system to about 4.3, and then the temperature of the system was cooled to about 10 oo. Next, after adding 5 parts of 25% glutaraldehyde, it was sufficiently aged to form 7 microcapsules with an average particle size (hereinafter, the average particle size indicates the body average particle size measured by Coulter Counter measurement) based on the solid content weight ratio. A capsule solution containing 14% was prepared. Briefly, 60 parts of water is added to 40 parts of a polyvinyl acetate emulsion with a solid content weight ratio of 60% and 12 parts of a 10% polyvinyl alcohol aqueous solution, and the mixture is stirred. Next, this emulsion was atomized into a pilot-type atomizer dryer manufactured by Bowen Engineering, Inc., and before the atomized particles were completely dried, three anchors of talc were injected from the cold air inlet. In addition, agglomerated fine particles having an average particle size of 28 were obtained. Add 50 parts of the above capsule solution, 5 parts of the fine particles, 1 part, 2 parts of the particles,
After being well dispersed, each of the liquids was coated on one side of the sheet at a dry weight of 5 coats/force to obtain capsule-coated paper (top paper). Separately, standard paper coated with an electron-accepting adsorbent material was prepared as follows. Q-methylstyrene polymer (average molecular weight 1100, softening point 110) 1000
A portion was heated and melted at 180°C. Among these, 3.5-di (Q
- 60 parts of zinc salt of Q-dimethylbenzyl salicylic acid was added and melted and mixed. This was cooled and solidified, then coarsely crushed, 500 parts of water was added, and the mixture was stirred.
10 parts and polyvinyl alcohol (Poval 117,
250 parts of a 10% aqueous solution (manufactured by Kuraray Co., Ltd.) was added thereto, and the mixture was pulverized using a continuous sand grinder. The concentration of the processing liquid is 24%
, the viscosity was 3&ps (1500). 40 parts of finely powdered zinc silicate and 100 parts of kaolin were added to the suspension thus obtained.
Ikarito, 200 parts of a 10% soluble starch aqueous solution, and 1,000 parts (solid content: 50%) of styrene-butadiene copolymer latex (304K, manufactured by Sumitomo Naugatuck) were added and mixed to obtain a paint. This coating solution was continuously coated on a base paper with a dry weight of 50 ta' by a blade coater and dried to obtain a colored paper (lower paper). In order to confirm the effects of the present invention, the capsule surface of the capsule-coated paper (upper paper) obtained as described above was superimposed on the front surface of the standard colored paper and a colored mark was obtained by applying a pressure of 40 kg'c. . Separately, using a Sutherland friction tester, the capsule surface of the upper paper was rubbed against the front surface of the lower paper 10 times to create a colored mark. Also, the upper paper and the lower paper were overlapped and struck with a striking machine to obtain a colored mark. The color densities of the weighted pressure marks and friction marks obtained in this way were measured using a Hitachi double beam spectrophotometer, and the color densities of the color marks produced by the striking machine were measured using a Macbeth densitometer (RD-1).
00R). The results are shown in the table. Note that the higher the value of the weighted pressure mark color density and friction mark color density described in this table and the following tables, the better the pressure resistance and abrasion resistance. The larger the value, the better the type color development. Table 1) As shown in this table, as the amount of added fine particles increases, the pressure resistance and abrasion resistance improve, and the coloring ability hardly decreases.

Example 2 An emulsion of butadiene-acrylonitrile copolymer emulsion with a solid content weight ratio of 55% was prepared by adding 40 parts of an anchor, 10% polyvinyl alcohol, 20 parts of water-soluble base, and 40 parts of water.
Before the mist-dried particulates were completely dried, talc 2
The base was added to obtain agglomerated fine particles having an average particle size of 35 mm.

The thus obtained fine particles were added to 500 parts of each of the capsule liquids obtained in Example 1 in 5 parts, 1 part, 15 parts, and 2 parts, respectively. The capsule-coated paper (upper paper) was obtained by applying the coating to a strength of 5.0 m/t. Using the obtained coating sheet, the effect was confirmed according to the same procedure as in Example 1, and the results are shown in Table 2.
It was shown to. Table 2) Example 3 An emulsion obtained by adding 40 parts of a vinyl acetate-acrylonitrile copolymer emulsion with a solid content weight ratio of 50% to 10 parts of a 10% hydroxymethylcellulose aqueous solution and 50 parts of water was prepared in Example 3. The particles were mist-dried using the apparatus described in 1, and before the particles were completely dried, a titanium dioxide trioxide was added through the cold air inlet to obtain agglomerated particles having an average particle size of 25 mm. .

Capsule-coated paper was obtained in the same manner as in Example 1 using the obtained polymer fine particles, and the effect was confirmed in the same manner as in Example 1. The results were as shown in Table 3.
Table 3) Target Example 1 Capsule-coated paper was obtained in the same manner as in Example 1, except that starch particles having an average particle size of 25 mm were used instead of the polymer fine particles in Example 1, and the same method as in Example 1 was used. The effectiveness was confirmed according to the procedure.

The results were as shown in Table 4. Table 4) As can be seen from this table, starch particles are effective in improving pressure resistance, but have no effect on pseudo resistance.

Target Example 2 2 parts of starch particles having an average particle size of 25 mm were added to 500 parts of each of the capsule liquid obtained in Example 1, mixed and dispersed well, and further 5 parts and 1 part of starch particles were added in terms of solid weight, respectively. Gelatinized starch of 15 parts, 15 parts, and 2 parts of Ikari was added, and each of these solutions was coated on one side of the sheet to a dry weight of 5.0 ta' to obtain capsule-coated paper.

Using the obtained capsule-coated sheet, the effect was confirmed according to the same procedure as in Example 1. The result was 0 for women in Table 5. Table 5) Target Example 3 The same procedure as Target Example 2 was carried out except that aluminum hydroxide having an average particle size of 2 was used instead of the starch particles in Target Example 2.

The results were as shown in Table 6. Table 6) Example 4 Example 1 except that a vinegar-peace-styrene copolymer emulsion was used instead of the polyvinyl acetate emulsion in Example 1.
Using fine particles having an average particle diameter of 30 mm obtained by spray drying in the same manner as in Example 1, the results shown in Table 7 were obtained.

Table 7) Example 5 Average particle size 25 obtained by spray drying in the same manner as in Example 1 except that a vinyl acetate-vinyl chloride copolymer emulsion was used instead of the polyvinyl acetate emulsion in Example 1. The same procedure as in Example 1 was carried out using fine particles having a structure, and the results shown in Table 8 were obtained.

Table 8)

Claims (1)

[Claims] 1 When an aqueous emulsion or suspension of a synthetic polymer contains a water-soluble polymer in an amount of 1 to 10% by weight based on the synthetic polymer and is spray-dried so that the polymer particles are in a wet solid state. By adding an inert substance to the microcapsules, the average particle size can be increased to 1.5 to 7 times the average particle size of the microcapsules.
1. A pressure-sensitive copying paper characterized in that agglomerated particles of the same size are obtained and dispersed in a microcapsule coating layer.