JPH0772266B2 - Pressure sensitive adhesive emulsion for carbonless paper - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive emulsion for carbonless paper used for pressure-sensitive adhesive sheets and the like.

[Conventional technology]

The conventional pressure-sensitive adhesive emulsion pressure-sensitive adhesive sheet does not contain the surfactant used during polymerization, so decoloring occurs in 1-2 days when the pressure-sensitive adhesive sheet is pasted on carbonless paper. , It was impossible to use because there was a problem that the destination, name, etc. were unknown.

[Problems to be Solved by the Invention]

Due to the above-mentioned difficulties, solvent-based acrylic or solvent-based natural rubber pressure-sensitive adhesives have been mainly used for this application, and water-based pressure-sensitive adhesive emulsions have never been used.

However, solvent-based pressure-sensitive adhesives have various problems such as toxicity and risk of ignition and environmental destruction, and the advent of a water-based emulsion-type pressure-sensitive adhesive that solves the above problems has been desired.

An object of the present invention is to provide a novel pressure-sensitive adhesive emulsion which eliminates the drawback of conventional emulsions that the characters disappear when they are attached to carbonless paper.

[Means for Solving the Problems]

That is, the present invention eliminates or minimizes the amount of the free surfactant present in the pressure-sensitive adhesive emulsion, which causes characters to disappear when a pressure-sensitive adhesive sheet is attached to carbonless paper, and In order to minimize the migration of
During emulsion polymerization, the following general formulas (I), (II), (II
It is characterized in that at least one of the reactive emulsifiers represented by I) is used in an amount of 0.05 to 20% by weight based on the total monomers.

M: alkali metal, ammonium, etc., n = 3 to 5 M: alkali metal, ammonium, etc., n = 10 to 20 R: alkyl group (C number: 4 to 20) R: alkyl group (C number: 4 to 20) The amount of the reactive emulsifier used is preferably as small as possible,
It is 0.05 to 20% by weight, more preferably 0.1 to 10% by weight, based on the system. If it is less than 0.05% by weight, the stability of the system during polymerization,
There is a problem in mechanical stability during coating. Also, 20% by weight
In the above, a large amount of free reactive emulsifiers (I), (II), (III) in the dry film (hereinafter referred to as reactive emulsifier)
Remains, which is a cause of hastening the disappearance of carbonless paper.

[Action]

In general, a method of polymerizing a vinyl monomer with a reactive emulsifier is a known fact, but an example of using it as a pressure-sensitive adhesive emulsion for carbonless paper is not known. The present invention provides a polymer emulsion emulsion-polymerized using a specific specific amount of a reactive emulsifier, in which there is almost no free surfactant in the emulsion, and therefore, a coating surface of a carbonless paper can be obtained. This is based on the finding that the disadvantage of disappearing characters without the migration of surfactants can be solved.

The present invention will be described in detail below.

The reactive emulsifier used in the present invention, M: alkali metal, ammonium, etc., n = 3 to 5 M: alkali metal, ammonium, etc., n = 10 to 20 R: alkyl group (C number: 4 to 20) R is an alkyl group (C number: 4 to 20).

As the polymer emulsion used in the present invention, any emulsion produced by any method can be used as long as it is an emulsion obtained by polymerizing a vinyl monomer in the presence of a predetermined amount of a reactive emulsifier. However, a method is preferred in which a vinyl monomer is preliminarily emulsified in the presence of a reactive emulsifier and water and then emulsion polymerization is performed.

The emulsion polymerization method is known, and conventional means is adopted in the present invention.

Specific examples of the vinyl monomer mentioned above include styrene and α
-Aromatic vinyl monomers such as methylstyrene and chlorostyrene, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic (Meth) acrylic acid esters such as butyl acrylate, 2-ethylhexyl (meth) acrylate, nonyl acrylate, etc., vinyl halides and vinylidene halides such as vinyl chloride, vinyl bromide, vinylidene chloride, vinylidene bromide, etc. , Vinyl acetates such as vinyl acetate and vinyl propionate, conjugated dienes such as butadiene and isoprene, olefins such as ethylene and propylene, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and salts thereof. Maleic acid,
Unsaturated polycarboxylic acids such as fumaric acid, itaconic acid, citraconic acid and hymic acid; monoesters of unsaturated polycarboxylic acids; salts of unsaturated polycarboxylic acids; acrylamide, methacrylamide, N-methylacrylamide, etc. Amides such as; allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, sodium allyl sulfonic acid, sodium methallyl sulfonic acid,
Sulfonated unsaturated hydrocarbons such as sodium styrene sulfonate and sodium vinyl sulfonate, and salts thereof; alkyl acrylamides such as 2-acrylamido-2-methylpropanesulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid sodium Sulfonic acid derivatives and salts thereof; quaternary ammonium salts such as N-methylvinylpyridinium chloride and 2-hydroxy-3-methacryloyloxypropyltrimethylammonium chloride; unsaturated ester salts such as alkylallyl sulfosuccinic acid sodium salt; 2-hydroxyethyl acrylate, 2
Unsaturated hydroxyl esters such as -hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and the like. These vinyl monomers may be used alone or in combination of two or more.

The carbon-free pressure-sensitive adhesive emulsion of the present invention is a polymer emulsion as it is or as the case requires, a crosslinking agent such as an epoxy resin, an isocyanate compound or an aziridine compound; a metal ion crosslinking agent such as an inorganic salt of calcium, magnesium or zinc. You may use it, adding additives, such as an agent, a thickener, a defoaming agent, and a cissing inhibitor.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples. Parts and% in the examples are by weight unless otherwise specified.

Example 1 A flask equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser was charged with 1 part of sodium pyrophosphate and 250 parts of water,
After raising the internal temperature to 80 ° C, 2-ethylhexyl acrylate 400 parts, methacrylic acid methyl acid 95 parts, methacrylic acid 5 parts, After adding 10 parts of a reactive emulsifier (50%) having a structure of n = 3 to 5 and 206 parts of water to completely emulsify the monomer in advance, it is kept constant for 4 hours together with 30 parts of 10% ammonium persulfate. Dropped at a rate. After the dropwise addition was completed, the temperature was maintained for 1.5 hours and stirring was continued to terminate the reaction. After cooling, the pH was adjusted by adding 3 parts of aqueous ammonia to obtain a milky white polymer emulsion. The pH of the obtained emulsion is 8.2,
The solid content concentration was 50.5%, and the viscosity was 500 cps (30 ° C, BH type).

Examples 2 to 3 Polymerization was carried out in the same manner as in Example 1 except that the amount of the reactive emulsifier was increased in the production of Example 1.

Examples 4 to 5 Reactive emulsifier in the preparation of Example 1 Polymerization was carried out in the same manner as in Example 1 except that the amount was changed in combination.

The amount, combination and properties of the reactive emulsifiers are shown in Table I.

Example 6 Polymerization was carried out in the same manner as in Example 1 except that the type of reactive emulsifier was changed in the production of Example 1.

Table II shows the types, amounts and properties of the reactive emulsifiers.

Non-reactive emulsifier _{C 9 H 19 (CH 2 CH} 2 O n SO 3 NH 4 n = 14~20 (50%) of using 1 part to monomer instead of the reactive emulsifier of Comparative Example 1 Example 1 Where polymerization was performed,
A milky white polymer emulsion having a solid content concentration of 50.5% and a viscosity of 500 cps (30 ° C., BH type) was obtained.

Comparative Examples 2 to 3 Polymerization was carried out in the same manner by increasing the amount of the emulsifier used in Comparative Example 1 as shown in Table III.

Comparative Example 4 For the emulsifier of Comparative Example 1 A non-reactive emulsifier having the structure of was also used in combination with 4 parts of the monomer, and polymerization was carried out in the same manner.

Comparative Examples 5 to 6 Polymerization was carried out similarly except that the amount of the reactive emulsifier used in Example 1 was outside the range of the present invention as shown in Table III.

The emulsions obtained in the respective examples and comparative examples were subjected to 15000 cps using Primal ASE-60 (produced by Rohm & Haas).
After thickening (30 ℃, BH type) to release paper and drying, 5
A sample was prepared by transferring to a 0 μ polyethylene film.

Comparative Example 7 A sample was prepared in the same manner as above using a solvent-based natural rubber pressure-sensitive adhesive currently used in the market.

Comparative Example 8 A sample was prepared in the same manner as above using a solvent-based acrylic pressure-sensitive adhesive currently used in the market.

Table IV shows the results of bonding the above sample to carbonless paper and leaving it for 2 weeks under the conditions of 20 ° C. and 65% RH.

[Effects of the Invention] According to Table IV, the pressure-sensitive adhesive emulsion of the present invention is very excellent in that it does not erase the characters of carbonless paper, and is suitable for solvent-based acrylic or solvent-based natural rubber pressure-sensitive adhesives. It is clear that it has comparable performance.

Claims (1)

[Claims] 1. A vinyl monomer is emulsified by using at least one of the reactive emulsifiers represented by the following general formulas (I), (II) and (III) in an amount of 0.05 to 20% by weight based on all monomers. Pressure-sensitive adhesive emulsion for carbonless paper, which is mainly composed of polymer emulsion obtained by polymerization M: alkali metal, ammonium, etc., n = 3 to 5 M: alkali metal, ammonium, etc., n = 10 to 20 R: alkyl group (C number: 4 to 20) R: Alkyl group (C number: 4 to 20)