JPS61268481A - Latex for pressure-sensitive manifold paper - Google Patents

Abstract

PURPOSE:To increase the degrees of blue color development and black color development, by preparing latex for pressures-sensitive manifold paper from specified quantities of aliphatic conjugated diolefin, ethylene unsaturated carboxylic acid and another monoolefin monomer being copolymerizable. CONSTITUTION:Synthetic copolymer latex for pressures-sensitive manifold paper is obtained by polymerizing aliphatic conjugated diolefin 35-60wt%, ethylene unsaturated carboxylic acid 6-19wt% and another monoolefin monomer 21-59wt%, which is copolymerizable with these substances, by a batch polymerization system or a continuous polymerization system. The swell index of a latex film formed of this copolymer latex is 5-30, and under-leaf paper is formed by applying the copolymer latex as an adhesive, together with a developer, on one surface of a base. As for the developer, an inorganic developer such as acid clay or active clay or an organic developer such as polyvalent metal salt of phenolic resin is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a synthetic copolymer latex that provides excellent blue and black coloring properties as a pressure-sensitive copying paper.

[Prior Art] In recent years, pressure-sensitive copying paper has shown a remarkable growth in demand with the rationalization of office work, the development of the information industry, and the spread of computers, and its uses have also been diversifying.

The most important physical property required of pressure-sensitive copying paper is color development, which is the essence of pressure-sensitive copying paper.

Color-forming refers to paper coated with fine capsules containing an electron-donating colorless or light-colored leuco dye dissolved in an organic solvent (capsule oil), an electron-accepting color developer, and an adhesive. The two coated surfaces, each consisting of a bottom paper with a color developing layer on the surface containing leuco dye, are placed facing each other, and printing pressure is applied to destroy the capsule, and the capsule oil containing the leuco dye is transferred to the color developing layer. The leuco dye and the color developer exhibit a color-forming reaction.

Currently, the most popular colors in the market are blue and black.

Synthetic copolymer latexes conventionally used as compositions for pressure-sensitive copying paper are disclosed in, for example, Japanese Patent Publication No. 19475/1983, Japanese Patent Application Laid-open No. 31405/1983, and Japanese Patent Application Laid-open No. 51-1989.
It is described in Publication No. 5119 and the like.

Japanese Patent Publication No. 5B-19475 and Japanese Patent Application Publication No. 53-314
What is stated in Publication No. 05 is that color development is significantly improved in the high gel content region, and JP-A No. 51-5119 discloses that unsaturated nitrile monomers are used. By doing so, the color development is improved.

As a result of examining the relationship between synthetic copolymer latex and color development, the present inventors found that synthetic copolymer latex with a high gel content significantly improves blue color development, while conversely, black color development significantly improves. It was found that the surface adhesion strength also decreased. It has also been found that unsaturated nitrile monomers improve black color development and reduce blue color development.

That is, it has been found that when a conventional synthetic copolymer latex is used as an adhesive for a lower sheet for pressure-sensitive copying paper, blue color development and black color development are completely inversely correlated.

[Problem that the invention seeks to solve]

As mentioned above, when conventional synthetic copolymer latex is used as an adhesive for lower paper for pressure-sensitive copying paper, blue coloration and black coloration exhibit contradictory phenomena.
It will be understood that it is extremely difficult to improve both properties without the benefit of one in the case of conventional synthetic copolymer latexes.

An object of the present invention is to provide a synthetic copolymer latex that can be used as a pressure-sensitive copying paper and simultaneously imparts excellent blue color development and black color development.

The inventors of the present invention have conducted intensive research to simultaneously improve blue color development and black color development of pressure-sensitive copying paper. As a result, by specifying the amount of ethylenically unsaturated carboxylic acid in the synthetic copolymer latex and the swell index of the latex film, the technical problem of simultaneously improving blue and black color development, which had been considered difficult in the past, was solved at once. I found something to do. Furthermore, the present inventors surprisingly discovered that when the amount of unsaturated carboxylic acid in the synthetic copolymer latex and the swell index of the latex film are defined, adhesive strength is also exhibited, leading to the completion of the present invention.

[Means and effects for solving the problems] The present invention comprises 35 to 60% by weight of aliphatic diolefin, 6 to 19% by weight of ethylenically unsaturated caldicic acid, and other monoolefin monomers copolymerizable with these. consisting of 21 to 59% by weight,
Swell index of latex film is 5-30
This invention relates to a synthetic copolymer latex for pressure-sensitive copying paper.

The present invention will be explained in detail below.

The aliphatic conjugated diolefin used in the present invention includes:
Examples include butadiene and isoprene. Usually, these monomers provide a synthetic copolymer with moderate elasticity.

If it is less than 35% by weight, sufficient elasticity will not be obtained and adhesive strength will be insufficient. Moreover, if it exceeds 60% by weight, the blue coloring will be significantly reduced.

Examples of ethylenically unsaturated caldicic acids include anhydrides or monoalkyl esters of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and dicarboxylic acid. These ethylenically unsaturated caldic acids improve adhesiveness and also improve blue color development and black color development.

When the amount is less than 6% by weight, improvements in these physical properties are observed. When the amount exceeds 19% by weight, the improvement in these physical properties becomes saturated and the amount of residue after producing the synthetic copolymer latex rapidly increases.

Monoolefin monomers that can be copolymerized with these include aromatic vinyl monomers such as styrene, α-methylstyrene, male nyltoluene, methyl acrylate,
Acrylate monomers exemplified by ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hyroxyethyl acrylate, 2-hyroxyprobyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, 2-
Methacrylate monomers exemplified by hyPoxyethyl methacrylate, 2-hyroxyzolobyl methacrylate, chrycidyl methacrylate, acrylamide r1
Examples include N-methylol acrylamide and acrylonitrile.

These are easily copolymerized with the aliphatic conjugated diolefin and the ethylenically unsaturated carboxylic acid monomer, and these monomers are usually used in an amount of 34 to 46 parts by weight.

The swell index of the synthetic copolymer latex film of the present invention ranges from 5 to 30. When the swell index is less than 5, adhesive strength decreases and black coloring is significantly reduced. On the other hand, when it exceeds 30, the blue coloring decreases significantly.

Chain transfer agents are important chemicals for adjusting the swell index of synthetic copolymer latex films.

Commonly used chain transfer agents include, for example, tr-decyl mercaptan, carbon tetrachloride, bromoform, and thioglycolic acid.

Further, these chain transfer agents may be used alone or in combination of two or more. Furthermore, the addition method may be either a batch addition method or a continuous addition method.

In order to obtain the synthetic copolymer of the present invention, as an emulsifier,
Anionic ones are best. Anionic surfactant is normal Cal7+? Any material used for producing the xyl-modified styrene-butadiene copolymer latex may be used, such as higher alcohol sulfuric esters, alkylbenzene sulfonates, aliphatic sulfonates, and the like.

In order to obtain the synthetic copolymer of the present invention, the polymerization initiator is a water-soluble initiator such as sodium persulfate, potassium persulfate, or ammonium persulfate, an oil-soluble initiator such as benzoyl peroxide, or Any initiator can be used. Further, if necessary, chelating agents, inorganic salts, etc. known for emulsion polymerization may be used.

The polymerization method of the synthetic copolymer latex of the present invention may be either a 1.6-inch polymerization method or a continuous polymerization method.

The synthetic copolymer latex thus obtained is applied as an adhesive along with a color developer to one side of a substrate to form a base paper.

Color developers include inorganic color developers such as acid clay, activated clay, calcined activated clay, etc., phenolic compounds, phenolic resins, maleic acid-rosin resins, partially or fully hydrolyzed styrene-maleic anhydride. Copolymer, polyvalent metal salt of phenolic resin, aromatic carboxylic acid-aldehyde
Organic color developers such as polymeric polyvalent metal salts and the like can be used.

In addition to the synthetic copolymer latex, in order to sufficiently retain pigments and various additives other than the color developer, starches, casein, gelatin, gum arabic, hollyhinyl alcohol, methyl cellulose, ethyl cellulose, etc. are usually used. Adhesives are also shared.

Pigments that can be used in the present invention include clay, titanium dioxide, satin white, calcium carbonate, and magnesium hydroxide.

Various additives that can be used in the present invention include antifoaming agents, waterproofing agents, lubricants, dispersants, etc., which are commonly used in the field of paper coating.

When the synthetic copolymer latex of the present invention is used as an adhesive for lower paper for pressure-sensitive copying paper, it is preferably used in an amount of 5 to 25 parts by weight per 100 parts by weight of pigment and color developer. If the amount of synthetic copolymer latex used is less than 5 parts by weight, the surface adhesive strength of the bottom paper for pressure-sensitive copying paper will be significantly inferior. On the other hand, if the amount exceeds 25 parts by weight, both blue color development and black color development are significantly reduced.

〔Effect of the invention〕

When the unique synthetic copolymer latex of the present invention was used as an adhesive for lower paper for pressure-sensitive copying paper, it imparted extremely excellent blue and black coloring and exhibited excellent adhesive strength. Copy paper can be provided.

〔Example〕

Next, examples and comparative examples will be shown. The numbers 2 and parts below are by weight unless otherwise specified.

The method for measuring each physical property in Examples and Comparative Examples is as follows:
The following is an example.

(1) Adhesive strength of coated paper: Using an RI printing tester manufactured by Mei Seisakusho Co., Ltd., overprinting was performed several times with ink of tack 10.
Visually judge the picking state of the printed surface. Larger numbers are better.

(2) Color development of coated paper: Layer a lower paper containing each synthetic copolymer latex and a commercially available upper paper, and apply printing pressure using a GT tester. (Printing pressure: 35 mm, spring M) After 30 seconds of color development, the color density was measured using a Hunter whiteness meter. Lower numbers are better.

(3) Latex film is formed at room temperature for 24 hours in an atmosphere with a swell index of 23° C. and 65% RH. This product is immersed in a luene solution of about 0.52 and JJ30z), stirred and dissolved in a shaker for about 4 hours, and filtered through a 200-mesh wire mesh. It is expressed as a ratio between the weight of the toluene-containing residue filtered on a wire mesh and the weight of the residue after drying.

Examples 1 to 6, Comparative Examples 1 to 6 1) Synthetic copolymer latex In Example 1, 40 parts of butadiene, 8 parts of acrylic acid, 3 parts of itaconic acid, 49 parts of styrene, 4 parts of carbon tetrachloride, and sodium hydrogen carbonate. 0.9 parts of potassium persulfate, 0.5 parts of sodium alkylbenzenesulfonate, and 150 parts of polymerized water were placed in an autoclave and reacted for 9 hours at 80°C while stirring in a nitrogen atmosphere. Ta. The polymerization conversion rate of monomers was 99.5%.

In Comparative Example 1, 9 parts of carbon tetrachloride was used under the above conditions to obtain a synthetic copolymer latex. The polymerization conversion rate of monomers was 99.6%. The monomer compositions of other examples and comparative examples of the synthetic copolymer latex are as shown in Table 1, and the listed parts were polymerized under the same polymerization conditions as above,
Each synthetic copolymer latex was obtained. The pH of the synthetic copolymer latex was adjusted to 8 with sodium hydroxide, and water vapor and nitrogen blowing were performed to remove residual monomers to obtain a desired synthetic copolymer latex. The average particle size of this copolymer is approximately 1600X uniform.

2) Evaluation as a bottom sheet for pressure-sensitive copying paper The following coating solution was prepared, and this coating solution was applied to one side of a 5oy7m2 sheet of paper to a dry weight of 517m2.
It was dried to obtain a paper sheet.

Clay 80 parts Sodium polyacrylate 0.5 NaOH 0.5 Oxidized starch 6 Synthetic copolymer latex 12 Solid content (wt%) 30 Coated surface of lower paper obtained in Examples 1 to 6 and Comparative Examples 1 to 6 A color development test was conducted by stacking commercially available paper sheets so that the coated sides were facing each other. Furthermore, the adhesion strength of the coated surface of the bottom paper itself was evaluated using an RI printing machine. The results are shown in Table 2.

Below margin Table 1 Table 2

Claims (2)

[Claims] (1) A latex film consisting of 35 to 60% by weight of aliphatic conjugated diolefin, 6 to 19% by weight of ethylenically unsaturated carboxylic acid, and 21 to 59% by weight of other monoolefin monomers copolymerizable with these. A synthetic copolymer latex for pressure-sensitive copying paper having a swell index of 5 to 30. (2) A composition for pressure-sensitive copying paper, characterized in that it contains 5 to 25 parts by weight of the synthetic copolymer latex described in claim 1 per 100 parts by weight of the pigment and color developer.