JPH03207781A - Pressure sensitive adhesive emulsion for carbonless paper - Google Patents

Abstract

PURPOSE:To obtain the novel title emulsion consisting essentially of a polymer emulsion obtained by subjecting a vinyl monomer to emulsion polymerization using a reactive emulsifying agent, free from causing loss of characters written on a carbonless paper and used for tacky sheet, etc. CONSTITUTION:The aimed emulsion consisting essentially of a polymer emulsion obtained by subjecting a vinyl monomer to emulsion polymerization using a reactive emulsifying agent consisting of a surfactant containing a double bond such as allyl group, (meth)acrylic acid group or maleic acid group in a molecule at an amount of 0.05-20wt.% (preferably 0.1-10wt.%) based on the system. Furthermore, the emulsion is preferably obtained by a method applying pretreatment previously emulsifying the vinyl monomer and water in the presence of a reactive emulsifying agent to the vinyl monomer and then subjecting the treated vinyl monomer to emulsion polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure-sensitive adhesive emulsion for carbonless paper used in adhesive sheets and the like.

[Conventional technology]

In conventional pressure-sensitive adhesive emulsion-based adhesive sheets for courier services, the surfactant used during polymerization exists freely, so when the adhesive sheet is pasted onto carbonless paper, decolorization occurs within 1 to 2 days. , the address, name, etc., were unclear, making it unusable.

[Problem to be solved by the invention]

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

However, solvent-based pressure-sensitive adhesives have various problems such as toxicity, flammability, and environmental damage, and it has been desired to develop a water-based emulsion-type pressure-sensitive adhesive that can solve the above-mentioned problems.

An object of the present invention is to provide a new pressure-sensitive adhesive emulsion that overcomes the drawback of conventional Emulzigin, which is that characters disappear when laminated to carbonless paper.

[Means to solve the problem]

That is, the present invention eliminates or minimizes the amount of free surfactant present in the pressure-sensitive adhesive Emulgylan, which causes letters to disappear when an adhesive sheet is attached to carbonless paper, and allows it to be applied to the coating surface. In order to minimize the migration of
It is characterized by the use of a reactive emulsifier during emulsion polymerization.

It is preferable that the amount of reactive emulsifier used be as small as possible.
0.05 to 20% by weight, more preferably 0.05 to 20% by weight based on the system.
1 to 10% by weight. If the amount is less than 0.05%, problems will arise in the stability of the system during polymerization, mechanical stability during coating, etc. Moreover, if it exceeds 20% by weight, a large amount of free reactive emulsifier remains in the dry film, which causes the characters on carbonless paper to disappear more quickly.

[For production]

Generally, the method of polymerizing vinyl monomers with a reactive emulsifier is a well-known fact, but there is no known example of its use as a pressure-sensitive adhesive emulsion for carbonless paper. The present invention is characterized in that a polymer emulsion polymerized by emulsion polymerization using a specific amount of a reactive emulsifier has almost no free surfactant in the emulsion, and therefore has no surface activity on the coated surface of carbonless paper. This is based on the knowledge that there is no migration of the agent and the problem of character disappearance is resolved.

The present invention will be explained in detail below.

The reactive emulsifier used in the present invention is a surfactant that contains a double bond such as an allyl group, (meth)acrylic group, or maleic acid in its molecule and is capable of radical polymerization. Specific examples include the following compounds. can be mentioned.

CH2-COOR2 R1 1 Cll-COO-CH2-C-CH,, SO3M Rl: H or CH3 R2: Alkyl group M: Alkali metal, ammonium, etc. CH-COOCH2-CHCH20-CH2Cl 閤CH
2S03M OH R: Alkyl group M: Alkali metal, ammonium, etc. R: Alkyl group 0 - (CM20) n-So3Nan: 10-20 Those having the structures (1) to [V] above are generally well known at present. Although it is a reactive emulsifier, it goes without saying that those having other structures are also included in the present invention.

The polymer emulsion used in the present invention can be produced by any method as long as it is obtained by polymerizing a vinyl monomer in the presence of a predetermined amount of a reactive emulsifier. However, it is preferable to carry out emulsion polymerization after pretreatment of emulsifying the vinyl monomer in the presence of a reactive emulsifier and water.

Emulsion polymerization methods are well known, and conventional means are employed in the present invention.

Specific examples of the vinyl monomer mentioned above include styrene, α
- Aromatic vinyl monomers such as methylstyrene, chlorostyrene, etc., vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, etc., methyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylic (meth)acrylic acid esters such as butyl acid, 2-ethylhexyl (meth)acrylate, nonyl acrylate, etc., vinyl halides and vinylidene halides such as vinyl chloride, vinyl bromide, vinylidene chloride, vinylidene bromide, etc. vinyl esters such as vinyl acetate and vinyl brobionate; conjugated dienes such as butadiene and isobrene; olefins such as ethylene and propylene; unsaturated monocarboxylic acids and their salts such as acrylic acid and methacrylic acid; ; Unsaturated polycarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, hymic acid, etc.; Monoesters of unsaturated polycarboxylic acids; Salts of unsaturated polycarboxylic acids; Acrylamide, methacrylamide, N - Amides such as methylacrylamide; sulfones such as allylsulfonic acid, metaallylsulfonic acid, styrenesulfonic acid, vinylsulfonic acid, sodium allylsulfonate, sodium metaallylsulfonate, sodium styrenesulfonate, sodium vinylsulfonate, etc. unsaturated hydrocarbons and their salts; alkylsulfonic acid derivatives of acrylamide such as 2-acrylamido-2-methylbrovanesulfonic acid and sodium 2-acrylamido-2-methylbrovanesulfonate and their salts; N-methylvinylpyri Quaternary ammonium salts such as dium chloride, 2-hydroxy-3-methacryloyloxyprobyltrimethylammonium chloride; unsaturated ester salts such as alkylarylsulfocono\sodium chloride; 2-hydroxyethyl acrylate, 2-hydroxy Examples include unsaturated hydroxyl esters such as brobyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxybrobyl methacrylate. These vinyl monomers may be used alone or in combination of two or more.

The carbonless pressure-sensitive adhesive emulsion of the present invention can be prepared by using a polymer emulsion as it is or, if necessary, using a crosslinking agent such as an epoxy resin, an isocyanate compound, or an aziridine compound; or a metal ion crosslinking agent such as an inorganic salt of calcium, magnesium, or zinc. Additives such as thickeners, thickeners, antifoaming agents, and anti-cissing agents may also be used.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples. Note that parts and percentages in the examples are based on weight unless otherwise specified.

Example 1 Into a flask equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, 1 part of sodium birophosphate and 250 parts of water were charged, and after raising the internal temperature to 80°C, 2-ethylhexyl acrylate was added. 400 parts of methyl methacrylate, 95 parts of methacrylic acid, 10 parts of a reactive emulsifier (50%) having a structure of nwa = 3 to 5, and 206 parts of water were added to completely emulsify the monomers in advance. Thereafter, 30 parts of 10% ammonium persulfate was added dropwise over a period of 4 hours at a constant rate. After the completion of the dropwise addition, the temperature was maintained for 1.5 hours and stirring was continued to complete the reaction. After cooling, 3 parts of ammonia water was added to adjust the pH to obtain a milky white polymer emulsion. The pH of the obtained emulsion was 8.2, the solid content concentration was 50.5%, and the viscosity was 500 cps (10°C, B
H type).

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

Examples 4 to 5 Polymerization was carried out in the same manner as in Example 1 except that the reactive emulsifier 0(CH20)2oH was used in combination and the amount was varied.

The amounts and combinations of reactive emulsifiers used and their properties are shown in Table 1.

Examples 6 to 9 Polymerization was carried out in the same manner as in Example 1, except that the type of reactive emulsifier was changed.

The type, amount used, and properties of the reactive emulsifier are shown in Table 1.

Comparative Example 1 Non-reactive emulsifier R instead of the reactive emulsifier of Example 1
When polymerization was carried out using 1 part of O(CH2CH20)nS03NH4 (50%) based on the monomer, the solid content concentration was 50.
．． 5% and a viscosity of 500 cps (30° C., BH type), a milky white polymer emulzidine was obtained.

Comparative Examples 2-3 Polymerization was carried out in the same manner as in Comparative Example 1, with the amount of emulsifier increased as shown in Table 1.

Comparative Example 4 Polymerization was carried out in the same manner as in Comparative Example 1 using a non-reactive emulsifier having a structure similar to that of Comparative Example 1 in combination with 4 parts of the monomer.

Comparative Examples 5-6 Polymerizations were carried out in the same manner as in Example 1 except that the amount of reactive emulsifier used was outside the scope of the present invention as shown in Table H.

Emulzidine obtained in each Example and Comparative Example was treated with Brimar ASE-60 (manufactured by Rohm & Haas) for 15 minutes.
The viscosity was increased to 000 cps (80° C., BH type), applied to a release paper, dried, and then transferred to a 50μ polyethylene film to prepare a sample.

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

The above sample was pasted on carbonless paper and heated at 20°C. 85%R
The results of leaving the sample for 2 weeks under the conditions of l{ are shown in Table ■.

Table■ Criteria for evaluation 5: No change at all or slight fading 4: Fading of the characters is visible, but there is no problem with legibility 3: Limit of character legibility 2: Most of the characters have disappeared 1: They have completely disappeared [Effects of the Invention] According to Table 1, the pressure-sensitive adhesive Emulzidine of the present invention is excellent in that the characters on carbonless paper do not disappear, and it is superior to solvent-based acrylic or solvent-based natural rubber pressure-sensitive adhesives. It is clear that the performance is comparable to that of

Claims (1)

[Claims] A pressure-sensitive adhesive emulsion for carbonless paper, which is mainly composed of a polymer emulsion obtained by emulsion polymerization of vinyl monomers using 0.05 to 20% by weight of a reactive emulsifier based on the total monomers.