JPH01146977A - Pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To obtain a pressure-sensitive adhesive which can be easily repeeled, and leaves no adhesive on the surface of an article after repeeling, by dissolving a copolymer obtained by graft-polymerizing a specified polymer with a polysiloxane in an organic solvent. CONSTITUTION:A graft copolymer (A) of a weight-average MW of 100000-1000000 is obtained by graft-polymerizing a polymer (a) based on an alkyl (meth)acrylate, of a glass transition point (a peak value of tansigma in a viscoelasticity spectrum) <=-20 deg.C (e.g., poly-n-butyl acrylate) with 1-25wt.% polysiloxane (b) (e.g., dimethylpolysiloxane having a methacryloxypropyl group on one end) of a degree of polymerization of 5-500 and an average MW of 1000-50000. Component A is dissolved in an organic solvent to obtain a pressure-sensitive adhesive. This pressure-sensitive adhesive is applied to either surface of a 10-80mu-thick base film prepared from a thermoplastic resin, paper or the like, and dried by heating to obtain a pressure-sensitive film having a pressure-sensitive adhesive layer of a thickness of 5-30mu.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an adhesive suitable for use in adhesive films that require removability, such as surface protection films.

(Prior art) Adhesive films, in which a removable adhesive layer is formed on one side of a base film made of thermoplastic resin such as polyolefin or paper, can be used, for example, as a surface protection film, on metal plates, synthetic resin plates, decorative It is used to temporarily attach to the surface of items such as plywood and temporary glass to protect the surface from dust and scratches.

This type of removable adhesive film requires improvements in the adhesive layer, especially in terms of adhesion when pasted on various articles, removability when peeled off from articles, stain resistance, and adhesive residue. ing.

As such a removable adhesive film, for example,
No. 7-30729 discloses that an aqueous emulsion composition containing a water-soluble silicone oil in an aqueous emulsion of a copolymer containing an acrylic acid alkyl ester as a main component is coated on one side of a base film, and the composition is heated and dried. A surface protection adhesive film having an adhesive layer formed of a crosslinked acrylic copolymer has been disclosed.

When the above-mentioned adhesive film is used, the surface of the adhesive layer is appropriately inactivated by the water-soluble silicone oil present in the adhesive layer, and a suitable initial tackiness is maintained, and the tackiness does not increase over time. This improves adhesive residue and removability.

(Problems to be solved by the invention) However, in such a removable adhesive film,
There is a problem in that the water-soluble silicone oil gradually bleeds from the adhesive layer, and when the adhesive film is peeled off from the article, the water-soluble silicone oil adheres to the surface of the article, contaminating the surface of the article.

In particular, the article to which the adhesive film is attached is, for example, 60 to 8
This tendency is more pronounced when exposed to relatively high temperatures such as 0°C or when stored for a long period of time.

The present invention is intended to solve the above-mentioned problems, and aims to provide an article with appropriate initial tackiness, little increase in tackiness over time, easy re-peeling, and an article after re-peeling. To provide an adhesive that does not leave adhesive residue on the surface and does not cause staining.

(Means for Solving the Problems) The adhesive of the present invention is made of a graft copolymer in which polysiloxane is grafted onto a polymer containing (meth)acrylic acid alkyl ester as a main component. is achieved.

In the above-mentioned graft copolymer, the polymer whose main chain is a (meth)acrylic acid alkyl ester decreases in tackiness as the glass transition temperature increases, so it is indicated by the peak value of tanσ in the viscoelastic spectrum. The glass transition temperature is preferably -20°C or lower, more preferably -25°C or lower. As the (meth)acrylic acid alkyl ester which is the main polymerization component of such a polymer, those having an alkyl group having 4 to 12 carbon atoms are preferable from the viewpoint of obtaining the above-mentioned polymer having a low glass transition temperature. ) n-butyl acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, dodecyl (meth)acrylate, and the like are preferably used.

One or more types of such (meth)acrylic acid alkyl esters may be used, and only these (meth)acrylic acid alkyl esters may be used without using polymerization subcomponents. However, if necessary for the balance of adhesive force and cohesive force, polymerizable polar polymers such as (meth)acrylic acid, (meth)acrylamide, and 2-hydroxyethyl (meth)acrylate are generally added as polymerization subcomponents. It may be used in a range of 30% by weight or less.

In addition, in the above-mentioned graft copolymer, dimethylpolysiloxane is used as the side chain polysiloxane for boat fishing, but other types such as diphenylpolysiloxane, phenylmethylpolysiloxane, and methylhydrogen polysiloxane can also be used. can. Further, the above polysiloxane has a degree of polymerization of 5 to 500 and an average molecular weight of 1°00.
0 to 50.000 is preferable, more preferably 3
,000 to 20,000. Average molecular weight is 1,00
When it is less than 0, removability becomes poor.

Preferably, such polysiloxane is contained in the graft copolymer in an amount of 1 to 25% by weight.

If it is less than 1% by weight, the tackiness increases and re-peelability becomes poor, and if it exceeds 25% by weight, the tackiness decreases.

Such a graft copolymer is a so-called macromonomer having a radically polymerizable group such as a (meth)acrylate group, a vinyl group, or a styryl group at one end of a polysiloxane (for example, a so-called macromonomer having a methacryloxypropyl group at one end). It is obtained by graft polymerizing Silabrene FM 0721) manufactured by Chisso Corporation, which is a dimethylpolysiloxane, and the above-mentioned hetamine whose main component is an alkyl (meth)acrylic acid ester.

In addition, when a polymer containing (meth)acrylic acid alkyl ester as a main component has a carboxylic acid group or a hydroxyl group in the molecule, a reaction between a polysiloxane having a hydroxyl group or a carboxylic acid group at one end and a polyisocyanate, etc. It can also be obtained by combining with chemical species. and,
The weight average molecule (■) of the above graft copolymer is 100,000 to 10
It is preferably about 00,000, more preferably from 200,000 to
It is 800,000.

The graft polymer obtained in this way is generally dissolved in an organic solvent to make an adhesive, and is applied to one side of a base film made of a thermoplastic resin such as polyolefin or yam, and then heated and dried. , made with adhesive film. Also,
It is also possible to make an adhesive film by laminating it by melt coextrusion with a thermoplastic resin that forms a base film such as polyolefin, or by melt extruding it on one side of the base film or paper as described above. be. In addition, when a polyolefin film is used as the base film, it is preferable to increase the wetting tension by corona discharge treatment or the like.

In addition, the thickness of the base film and the adhesive layer may be determined as appropriate depending on the application, but the thickness of the base film is generally 10
~80μ, and the thickness of the adhesive layer is generally 5~30μ.
It will be done. In addition, a crosslinking agent, a softener, an ultraviolet absorber, an antioxidant, etc. may be added to the adhesive layer as necessary.

(Function) The adhesive of the present invention exhibits good adhesiveness due to the main chain of the polymer containing (meth)acrylic acid alkyl ester as a main component. Furthermore, the above-mentioned tackiness is suitably inactivated by the polysiloxane side grafted onto the main chain of the polymer, and the increase in tackiness over time is suppressed to a minimum.

Furthermore, since the side chains of the polysiloxane are chemically bonded to the main chain of the polymer whose main component is an alkyl (meth)acrylic ester by grafting, they do not separate and bleed.

(Example) Examples and comparative examples of the present invention are shown below.

In a backyard flame separable flask, 100 parts by weight of n-butyl acrylate, 2 parts by weight of acrylic acid, dimethylpolysiloxane having a methacryloxypropyl group at one end (silabrene FM 0721, average molecular weight: !!5,000, nitrogen) > 10 parts by weight, ethyl acetate 112 as a solvent
0.03 parts by weight of 1.1'-azobiscyclohexane-1-carbonitrile as a polymerization initiator, polymerization was carried out for 10 hours at the reflux temperature of ethyl acetate under a nitrogen atmosphere, and acrylic acid n A graft copolymer in which polysiloxane was grafted onto a -butyl-acrylic acid copolymer was obtained. The weight average molecular weight 1 (Mw) of this graft copolymer determined by gel permeation chromatography was about 750,000, and the glass transition temperature (Tg) indicated by the peak value of tanσ in the viscoelastic spectrum was about -30''C.

The above graft copolymer solution was returned to room temperature, and 2 parts by weight of a polyisocyanate crosslinking agent (Coronate I7, manufactured by Nippon Polyurethane Co., Ltd.) was added thereto to prepare an adhesive solution. As shown in Fig. 1, this adhesive solution was applied to one side of a 60 μm low-density polyethylene film 1 whose coated surface had been subjected to corona discharge treatment, and dried by heating at 80°C.
An adhesive film having a μ adhesive layer 2 formed thereon was manufactured.

Apply this adhesive film to the surface of a clean stainless steel plate at an angle of 20°.
Attached with a 2 kg pressure roller at C, 180° angular constant speed for this sample! ! Initial adhesion (20°C) and aging adhesion (20'C The condition (contamination) was observed and the results are shown in Table 1.

Actual ship pier 1 Silabrane I'M 0721.1 used in Example 1
The same procedure as in Example 1 was carried out except that 0 parts by weight was changed to 20 parts by weight. The results are shown in Table 1.

100 parts by weight of 2-ethylhexyl acrylate was used instead of 100 parts by weight of n-butyl acrylate used in Example 1, and 10 parts by weight of Silabrene FM 0721.1 was changed to 5 parts by weight. However, the same procedure as in Example 1 was carried out except for that. The results are shown in Table 1.

Example 1 was carried out in the same manner as in Example 1, except that Silabrene PM 0721 was not used at all. The results are shown in Table 1.

1 part by weight of dimethylpolysiloxane (SH200, manufactured by Toray Silicone) was added to the adhesive solution obtained in Comparative Example 1.
(parts by weight based on 100 parts by weight of n-butyl acrylate) was added, and the subsequent steps were performed in the same manner as in Example 1. The results are shown in Table 1.

(Margins below) Table 1 (Effects of the Invention) The adhesive of the present invention has a polysiloxane side chain introduced into the main chain of a polymer whose main component is an alkyl (meth)acrylic ester. The surface of the adhesive is suitably inactivated by the side chains of siloxane, maintaining appropriate initial tackiness, and exhibiting little increase in tackiness over time, making re-peeling easier and improving the surface of the article after re-peeling. No adhesive residue is left.

Since the above-mentioned polysiloxane is introduced by graft polymerization, this polysiloxane does not separate from the polymer whose main component is (meth)acrylic acid alkyl ester and bleed, and the product after re-peeling. No surface contamination occurs. In addition, it has good weather resistance and transparency, and has good anchoring properties to the base film.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an adhesive film using the adhesive of the present invention. 1-adhesive film, 2-adhesive. Figure 1

Claims (1)

[Claims] 1. An adhesive consisting of a graft copolymer in which polysiloxane is grafted onto a polymer whose main component is an alkyl (meth)acrylic acid ester.