JPH0757861B2 - Pressure-sensitive adhesive emulsion for surface protection sheet - Google Patents

Description

The present invention relates to a surface protection sheet for a metal plate such as a stainless plate, a steel plate and an aluminum plate, or an adhered plate such as a plastic plate, a glass plate and a decorative plate. It relates to a pressure sensitive adhesive emulsion suitable for use.

(Prior Art) Conventional surface protective sheets include paper or plastic films coated with an adhesive composition on one side, or an adhesive plate directly coated with an adhesive composition to form paper or plastic films. The one glued on it is commonly used.

However, the conventional surface protective sheet has too strong adhesive force to make peeling difficult, or the cohesive force increases with time to lose re-adhesiveness, and the adhesive composition is transferred to an adherend at the time of peeling. Then, there is a problem that the surface of the adherend is contaminated.

(Problems to be Solved by the Invention) A method of using a vinylyl compound or a diallyl compound in order to improve the above problems, a melamine resin, a cross-linking with an epoxy resin, or a cross-linking with a metal compound to reduce contamination on an adherend. There are ways to do it.

There is also a method of using a phosphoric acid ester-based surfactant or a reactive emulsifier as a surfactant used in emulsion polymerization to reduce the contamination of the adherend due to the leaching of the surfactant with time.

However, this type of pressure-sensitive adhesive composition has not sufficiently solved the drawback of contaminating the adherend. An object of the present invention is to provide a surface protective sheet which does not cause contamination of adherends, which is a drawback of emulsions, and does not increase in cohesive force with time and can be easily peeled off again.

(Means for Solving the Problems) That is, the present invention provides diallyl phthalate in an amount of 1 to 10% by weight based on all monomers.
Is a pressure-sensitive adhesive emulsion for a surface protective sheet, which is obtained by emulsion-copolymerizing a copolymerizable monomer mixture containing the following two steps.

First stage; without using emulsifier or water-soluble monomer
Emulsion polymerization of a monomer that does not contain diallyl phthalate produces seed emulsion particles in an amount of 1 to 10% by weight based on the total amount of the monomers. Second step; on the seed emulsion obtained in the first step, radically polymerizable active groups are added. The remaining emulsifier is used in an amount of 0.1 to 10% by weight based on all the monomers, and the remaining monomer mixture containing diallyl phthalate is emulsion-polymerized.

(Operation) The present invention will be described in detail below.

What is diallyl phthalate used in the present invention? And a copolymerizable monomer,
Styrene, styrene derivatives, vinyl esters, acrylic acid esters, methacrylic acid esters, acrylic acid,
Α, β-unsaturated carboxylic acids such as methacrylic acid and crotonic acid, or salts thereof, α, β-unsaturated amides such as acrylamide, methacrylamide, N-methylacrylamide, N-methylolacrylamide, acrylonitrile, methacryloyl Examples include nitrile, vinyl chloride, vinylidene chloride, α-olefin such as ethylene, conjugated diene such as butadiene, alkyl vinyl ethers, alkyl vinyl ketones, maleic anhydride, etc. These may be used alone or in admixture of two or more. Used. Among them, ethyl acrylate, butyl acrylate, 2
(Meth) acrylic acid esters such as ethylhexyl acrylate, 2-hydroxyethyl methacrylate, and methyl methacrylate and (meth) acrylic acid such as acrylic acid and methacrylic acid are preferable in terms of copolymerizability and physical properties. By adding diallyl phthalate to the monomer, it is possible to obtain a surface protective sheet which prevents the adherend from being contaminated and easily peels off without increasing the cohesive force with time.

The addition of diallyl phthalate is carried out in the second stage so as not to interfere with the formation of seed emulsion particles, and the amount used is 1 to 10% by weight based on the total monomers. When the amount used is 1% by weight or less, sufficient cohesive force cannot be obtained as a pressure-sensitive adhesive for a surface protection sheet. On the other hand, if it exceeds 10% by weight, the cohesive force is too high and the pressure-sensitive adhesive required for the surface protective sheet pressure-sensitive adhesive cannot be obtained. In the present invention, the stability of the emulsion is determined by forming the emulsion through two steps.
This is to improve the cohesive force and prevent contamination when used as an adhesive.

The method for producing seed emulsion particles by emulsion polymerization without using an emulsifier or a water-soluble monomer in the first step of the present invention is a known fact. It is produced by the method described in Japanese Examined Patent Publication No. 49-5615.

The seed emulsion produced in the first stage preferably has a ratio of 1 to 10% by weight, based on all the monomers. If it is 1% by weight or less, particles and the like necessary for the second stage polymerization cannot be obtained,
If it is more than 10% by weight, the desired stable emulsion cannot be obtained.

Next, the monomer mixture shown above is emulsion-polymerized on the seed emulsion obtained in the first step using an emulsifier having an active group capable of radical polymerization. Unless emulsion polymerization is carried out with an emulsifier having an active group capable of radical polymerization, the emulsifier will exist free in the water tank and cause contamination.

The emulsifier having a radically polymerizable active group is an emulsifier containing a double bond such as an allyl group, a (meth) acryl group, and maleic acid in the molecule. For example, eleminol JS-
2, (Sanyo Kasei Co., Ltd.), Latemuru S-180 (Kao Co., Ltd.) and the like. These may be used alone or in combination of two or more.

The use of an emulsifier having a radically polymerizable active group is to prevent contamination after peeling the sheet. The amount used is preferably in the range of 0.1 to 10% by weight based on all the monomers. If the amount used is 0.1% by weight or less, no sufficient effect can be obtained. On the other hand, if the amount used is 10% by weight or more, the adhesive strength is reduced or the adherend is contaminated.

Regarding the pressure-sensitive adhesive emulsion for the surface protective sheet of the present invention, if necessary, a filler such as clay, talc, calcium carbonate, titanium white, zinc white, an epoxy resin, an isocyanate compound, a cross-linking agent such as an aziridine compound, calcium. Ion cross-linking agents such as inorganic acid salts of magnesium, aluminum, zinc, butyl carbitol,
Addition of film-forming aids such as butyl carbitol acetate, plasticizers such as dibutyl phthalate and dioctyl phthalate, tackifiers such as rosin, terpene phenol, petroleum resin, thickeners, antifreezing agents, antifoaming agents, etc. You may add and use an agent.

The pressure-sensitive adhesive emulsion for surface protection sheet thus obtained is directly applied to a sheet or an adherend by a roll coater, a curtain coater or the like.

By using the method of the present invention, removability was made possible without an increase in adhesive strength over time, and contamination of the adherend surface could be eliminated.

Next, the present invention will be described with reference to examples. Parts indicate parts by weight.

Example 1 As a first step, 40 parts of ethyl acrylate, 0.004 of copper sulfate
4 parts, sodium thiosulfate 0.6 parts, potassium persulfate 0.4
Parts of water and 350 parts of water are subjected to ordinary emulsion polymerization at 50 ° C. for 30 minutes, and as a second step, 2 ethylhexyl acrylate 880
Parts, diallyl phthalate 60 parts, 2 hydroxyethyl methacrylate 12 parts, acrylic acid 25 parts, Eleminol JS-2
(Sanyo Kasei Co., Ltd.) 20 parts and potassium persulfate 1.5 parts were subjected to normal emulsion polymerization and the pH was adjusted to 8 with 28% ammonia water, and a high molecular weight ether type nonionic surfactant [Bissurf 1400 (Kao ( Co., Ltd.)] and adjusted to 2000 CPS to obtain a solid content of 5
A 0% polymer emulsion was obtained.

The pressure-sensitive adhesive composition is applied to the kraft paper surface with the thickness of the solid content.
It was coated so as to have a thickness of 20 μm and dried at 110 ° C. for 1 minute to obtain an adhesive film.

This adhesive film was attached to an acrylic plate, and the adhesive strength and the state of contamination on the acrylic plate were examined.

Examples 2 to 4 and Comparative Examples 1 to 7 Polymerization was performed in the same manner as in Example 1, and the pressure-sensitive adhesive was formed into a film in the same manner as in Example 1, and the adhesive strength and the state of contamination were examined.

(Effects of the invention) From Table 1, it is clear that the pressure-sensitive adhesive of the present invention is very excellent in that the adhesive force does not increase with time, the removability is good, and the adherend is not contaminated. Is.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // C08F 2/24 MCB 218/18 MLM

Claims (1)

[Claims] 1. A pressure-sensitive adhesive emulsion for a surface protective sheet, which is obtained by emulsion-copolymerizing a copolymerizable monomer mixture containing diallyl phthalate in an amount of 1 to 10% by weight based on all monomers. First stage; without using emulsifier or water-soluble monomer
Emulsion polymerization of a monomer that does not contain diallyl phthalate produces seed emulsion particles in an amount of 1 to 10% by weight based on the total amount of the monomers. Second step; on the seed emulsion obtained in the first step, radically polymerizable active groups are added. The remaining emulsifier is used in an amount of 0.1 to 10% by weight based on all the monomers, and the remaining monomer mixture containing diallyl phthalate is emulsion-polymerized.