JPH01139640A - Adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the title composition having moderate initial tack, little in tack promotion with time, easy to repeel, capable of melt extrusion, by incorporating a specific A-B-A block copolymer with a tacky resin consisting of specific graft (co)polymer. CONSTITUTION:The objective composition can be obtained by incorporating (A) 100 pts.wt. of an A-B-A block copolymer (A is styrene polymer block; B is butadiene polymer block, isoprene polymer block etc.) with (B) 5-100 pts.wt. of a graft copolymer where styrene (co)polymer has been grafted to (meth) acrylic ester (co)polymer.

Description

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

(Prior art) Removable adhesive films such as surface protection films, which have an adhesive layer formed on one side of a base film made of a thermoplastic resin such as polyolefin, are difficult to maintain adhesiveness when attached to various articles. It is desired to improve the adhesive layer, especially in terms of adhesive residue when peeled off from the article.

In addition, in the production of such adhesive films, from the standpoint of safety and hygiene, the adhesive composition is melt-extruded onto one side of the base film, or the adhesive composition and the thermoplastic resin of the base film are combined into a single piece of gold. A melt extrusion method is often adopted in which the components are melt-extruded together through mold slits to integrate them, and therefore there is a demand for adhesive compositions that are suitable for melt extrusion.

As this type of removable adhesive film, for example, Japanese Patent Publication No. 58-30911 and Japanese Patent Application Laid-Open No. 61-103975
In the publication, one side of a base film made of a thermoplastic resin such as polyolefin is coated with the general formula A-B-A' (however,
A represents a styrene polymer block, and B represents a butadiene polymer block, an isoprene polymer block, or an ethylene-butylene copolymer block. ) and rosin,
A surface protection film is disclosed in which a pressure-sensitive adhesive layer is formed by mixing a tackifier such as a petroleum resin. In this case, the tackifier has the function of developing tackiness.

(Problems to be solved by the invention) However, in such a removable adhesive film,
The initial adhesion is good, but the adhesion increases significantly over time. As a result, the surface protective film cannot be easily peeled off from the product after it has been used, requiring time and effort to remove it, and if it is removed too quickly, there are problems with adhesive residue and the base film stretching and breaking. .

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 its objectives are to have a suitable initial tackiness, little increase in tackiness over time, easy re-peelability, and melt extrusion. An object of the present invention is to provide a pressure-sensitive adhesive composition.

(Means for Solving the Problems) The adhesive composition of the present invention is a block copolymer of the general formula ABA (where A represents a styrene polymer block,
B represents a butadiene polymer block, an isoprene polymer block, or an olefin polymer block obtained by hydrogenating these. ) is characterized in that an adhesive resin consisting of a graft copolymer in which a styrene polymer or copolymer is grafted to a (meth)acrylic acid ester polymer or copolymer is mixed, thereby achieving the above-mentioned purpose. is achieved.

In the block copolymer of the above formula A-B-A,
Styrene polymer block A has an average molecular weight of 2,000
The glass transition temperature is preferably about 100,000 to 100,000, and the glass transition temperature is preferably 20°C or higher. The butadiene polymer block, isoprene polymer block, or olefin polymer block B obtained by hydrogenating these preferably has an average molecular weight of about to, ooo to 300,000, and has a glass transition temperature of about 100,000. 20°C
The following are preferred. In particular, an olefin polymer block B made of a saturated ethylene-butylene copolymer with no residual double bonds by hydrogenating a butadiene polymer block has excellent weather resistance and heat resistance, and is therefore suitable. used for.

The preferable weight ratio of the above A component and B component is A
/B = 5/95 to 50150, more preferably A/B = 10/90 to 30/70. As the block copolymer of the above formula A-B-A, Kraton G-1650, G-1652 manufactured by Shell Chemical Co., Ltd.
G-1657 and Califlex TR-1101, TR
-1107, Fintack manufactured by Nippon Zeon Co., Ltd., etc.

In addition, in the adhesive resin made of the above-mentioned graft copolymer, the side chain styrene polymer or copolymer preferably has an average molecular weight of about 3,000 to 20,000, and has a glass transition temperature of 20°C. The above are preferred. Examples of copolymerization components of the styrene copolymer include acrylonitrile, methyl methacrylate, phenylmaleimide, Schiff 1 hexylmaleimide, α-methylstyrene, and maleic acid, which are copolymerized in an amount of 40% by weight or less. is preferable.

Furthermore, since the adhesiveness of the main chain (meth)acrylic acid ester polymer or copolymer decreases as the glass transition temperature increases, it is preferable that the glass transition temperature is -20°C or lower. The (meth)acrylic acid ester which is a polymerization component of such a polymer or copolymer has 4 to 4 carbon atoms.
Those having 12 alkyl groups are preferred, such as n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, dodecyl (meth)acrylate, etc. is preferably used. As the copolymerization component of the above (meth)acrylic acid ester copolymer, polar polymers such as (meth)acrylic acid and (meth)acrylamide are preferably used, and are generally used in an amount of 30% by weight or less. .

In the adhesive resin made of the above graft copolymer, the weight ratio of the main chain (meth)acrylic acid ester polymer or copolymer component to the side chain styrene polymer or copolymer component is When the styrene polymer or copolymer component of the chain decreases, the compatibility with the above-mentioned A-B-A block copolymer decreases, and when it increases, the tackiness decreases, so the range of 70/30 to 9515 is preferred.

Further, the above graft copolymer has an average molecular weight of too
, ooo~L, about 000,000 is preferable,
More preferably, those having a molecular weight of 200,000 to 600,000 are used.

The adhesive resin made of such a graft copolymer is a so-called macromonomer having a radically polymerizable (meth)acrylate group at one end of the styrene polymer or copolymer (Chemlink 4500 Macromer manufactured by Sartomer Corporation in the United States, manufactured by Toagosei Kagaku Co., Ltd.). macromonomers AS-6, AN-6, etc.)
It is obtained by radical copolymerization of the above-mentioned hexamer and the above-mentioned hetamine whose main component is the (meth)acrylic acid ester.

Also, it has a carboxylic acid group or a hydroxyl group in the molecule (meth)
It can also be obtained by bonding an acrylic ester polymer or copolymer and a styrene polymer or copolymer having a hydroxyl group or carboxylic acid group at one end with a reactive chemical species such as polyisocyanate. .

The above graft copolymer is preferably mixed in an amount of 5 to 100 parts by weight with respect to 100 parts by weight of the block copolymer having the formula ABA. Less graft copolymer (
If the amount increases, the tackiness decreases, and if the amount increases, the tackiness increases and removability deteriorates.

The adhesive composition of the present invention can be laminated by coextrusion with a thermoplastic resin forming a base film such as polyolefin, melt-extruded onto one side of the base film or paper as described above, or melt-extruded into a film on one side of the base film or paper as described above. It is made into an adhesive film by dissolving it and applying it. Alternatively, without using a base film, the adhesive composition can be made into a film by melt extrusion or solvent casting onto a release paper.

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 is done. In addition, a softener, an ultraviolet absorber, an antioxidant, etc. may be added to the adhesive layer as necessary.

(Function) The pressure-sensitive adhesive composition of the present invention comprises a block copolymer of the general formula A-B-A, a (meth)acrylic acid ester polymer or copolymer, and a styrene polymer or copolymer grafted onto the block copolymer. By introducing the side chain of the styrene polymer or copolymer into the main chain of the (meth)acrylic acid ester polymer or copolymer, The compatibility with the above block copolymer is significantly improved. Therefore, it is possible to obtain a stable and homogeneous adhesive composition that is transparent as a whole and does not smear with the above-mentioned adhesive resin separated.

In addition, the adhesive resin made of the above graft copolymer is (
Since it contains a meth)acrylic acid ester polymerization component and a styrene polymerization component, it has excellent adhesiveness and heat resistance, which gives it a suitable initial adhesiveness, and also has little increase in adhesiveness over time or at high temperatures. , re-peeling becomes easy.

Furthermore, the adhesive composition of the present invention can be melt-extruded, has a strong anchoring force with a base film made of a thermoplastic resin such as polyolefin, and has good compatibility with the adhesive resin described above. , No contamination or adhesive residue occurs when re-peeling.

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

In a 1ffi separable flask with counterfeit soil, 400 g of n-butyl acrylate, 40 g of a styrene polymer having a methacrylate group at one end with a weight average molecular weight of FF 113.000 (Chemlink 4500?Chromer 1 manufactured by Sartomer, USA),
440 g of toluene was added as a solvent, 1 g of l,1'-azobiscyclohexane-1-carbonitrile was added as a polymerization initiator, and the mixture was heated at 90°C under a nitrogen atmosphere for 10 min.
After time polymerization, n-butyl acrylate polymer 100
A graft polymer having adhesive properties was obtained by grafting 10 parts by weight of a styrene polymer to the parts by weight. The weight average molecular weight of this graft copolymer determined by gel permeation chromatography was approximately 300,000.

-A block copolymer of formula A-B-A (Krayton G1
A toluene solution containing 80 parts by weight of the above-mentioned graft copolymer and 100 parts by weight of 657 (manufactured by Shell Chemical Co., Ltd.) was applied onto one side of a 60μ thick low-density polyethylene film and dried to form a 25μ thick low-density polyethylene film. A layer of the adhesive composition was formed to produce an adhesive film.

Apply this adhesive film to the surface of a clean stainless steel plate for 20"
For this sample, pasted with a 2 kg pressure roll at C.
180° angular constant speed peel strength test (tensile speed 300mm/
The initial adhesive strength (20°C) was measured. Also,
Regarding the above sample, it was held at 60°C for 50 hours, then returned to 20°C, and the high temperature aging adhesive strength (60
°C x 50 hours). The results are shown in Table 1.

The surface condition of the stainless steel plate after the measurement was observed, and the results are shown in parentheses.

In addition, a pressure-sensitive adhesive composition prepared by mixing 100 parts by weight of the above block copolymer with 80 parts by weight of a graft copolymer and low-density polyethylene (melt index 7 g/10 minutes) are coextruded to produce a 60-μ thick low-density polyethylene. An adhesive film was produced in which a 15 μm thick adhesive layer was formed on one side of a base film, and its melt extrudability was good.

1. 80 parts by weight of the graft copolymer used in Example 1, 20 parts by weight
The same procedure as in Example 1 was carried out except that the parts by weight were changed.

The results are shown in Table 1.

Same as Example 1 except that 80 parts by weight of n-butyl acrylate polymer having a weight average molecular weight of about 300,000 was used instead of 80 parts by weight of the graft copolymer used in Example 1. I went to The results are shown in Table 1.

Flame Comparison I Instead of 80 parts by weight of the graft copolymer used in Example 1, hydrogenated petroleum resin (Escolette 5 parts by weight) was used as a tackifier.
The same procedure as in Example 1 was carried out, except that 300 and 80 manufactured by Exxon Chemical Co., Ltd. were used in the mounting section. The results are shown in Table 1.

(Margin below) Table 1 (Effects of the Invention) Since the adhesive composition of the present invention is configured as described above, it has appropriate initial tackiness and exhibits improved tackiness over time and tackiness over time at high temperatures. It has good adhesive performance and removability with no adhesive residue even after aging.

Further, the adhesive composition of the present invention can be melt-extruded, has good weather resistance and transparency, and has excellent anchoring properties to non-polar base films such as polyolefin.

Claims (1)

[Claims] 1. A block copolymer of the general formula A-B-A (where A represents a styrene polymer block, and B represents a butadiene polymer block, an isoprene polymer block, or a hydrogenated product thereof) ) is mixed with an adhesive resin consisting of a graft copolymer obtained by grafting a styrene polymer or copolymer onto a (meth)acrylic acid ester polymer or copolymer. An adhesive composition characterized by: