JPS6011992B2 - Polyolefin adhesive tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single-sided or double-sided pressure-sensitive adhesive tape or sheet having a polyolefin foam as a support.

Because the surface of polyolefin foam has poor activity,
There is a problem in that the adhesiveness with the pressure-sensitive adhesive layer formed on the surface is insufficient.

In order to solve this problem, methods such as applying a primer to the foam surface or activating the foam surface are currently being used, but these methods are still insufficient. When a double-sided pressure-sensitive adhesive tape is used in applications that require high retention properties, such as adhesively fixing two hard articles, it has the disadvantage that it peels off at the interface between the foam surface and the adhesive layer.

In view of the state of the prior art, the present inventors have conducted various studies on double-sided pressure-sensitive adhesive tapes or sheets that can obtain high retention properties, and have found that a polyolefin foam whose surface has been activated has certain properties. The present inventors have found that the above requirements can be met by forming an adhesive film consisting of a mixture of a pressure sensitive adhesive composition having a polyisocyanate compound and a polyisocyanate compound.

That is, in the present invention, at least one surface of the polyolefin foam is activated to have a critical surface tension of at least 41 d/skin, and the treated surface has an apparent elastic modulus of 0.9 to 20 kg. The present invention provides a polyolefin adhesive tape in which an adhesive film made of a mixture of a block copolymer-based pressure-sensitive adhesive composition and a polyisocyanate compound is firmly bonded.

The polyolefin foam used in the practice of the present invention uses as a base material normally solid homopolymers of monoolefinically unsaturated hydrocarbons having 2 to 12 carbon atoms and copolymers thereof; This includes foaming agents, pigments,
It is foamed to about 2 to 5 needles by adding compounding agents such as fillers, and subjected to radiation crosslinking, chemical crosslinking, etc. as necessary. Examples of the above-mentioned homopolymer include polyethylene, polypropylene, polybutene-1, etc., and examples of the copolymer include ethylene-propylene copolymer,
Ethylene-pinyl acetate copolymer and the like are used. One or both sides of such polyolefin foams may be subjected to surface oxidizing treatments such as chromic acid treatment in sulfuric acid or hot nitric acid, ozone exposure treatment, high-voltage electric shock exposure treatment with corona discharge, ionizing radiation treatment, flame exposure treatment, etc. treatment to increase the critical surface tension to at least 41 dyne.
/ arc, preferably 44 to 5 yen/skin.

The surface of the foam to be oxidized is desirably made into a smooth skin layer by making the foam structure dense or by heat treatment. One or both sides of the activated polyolefin foam sheet or tape has a high apparent modulus of elasticity of 0.9 to 20k9', preferably 1.5 to 10k9/'. An adhesive film made of a mixture of a pressure-sensitive adhesive composition and a polyisocyanate compound is formed by means such as coating and drying, transfer, etc., and is used as the adhesive tape of the present invention. The pressure-sensitive adhesive composition used in the present invention has a high elastic modulus as described above, and is particularly suitable if it has strong adhesive strength to the surface to which it is applied under normal conditions or under heating at low temperatures. Although not limited, it is more preferable that the composition be substantially free of active hydrogen capable of reacting with NCO groups, or be a composition containing active hydrogen that is slow in reactivity.

According to the inventor's experiments, block copolymer rubbers such as styrene-isoprene-styrene block copolymer rubber, styrene-butadiene-styrene block copolymer rubber, and radial teleblock copolymer rubber are used as base materials. It has been found that pressure sensitive adhesive compositions are preferred because they have suitable modulus without containing active hydrogen that can react with NCO groups.

A polyisocyanate compound is blended into such a pressure sensitive adhesive composition to form a mixture.

It is desirable that the amount of the compound is in the range of 0.1 to 1 part by weight based on 10 parts by weight of the base material of the composition, and if it is less than 0.1 part by weight, the amount of the polyisocyanate compound The effect of addition is insufficient, and if it exceeds 10 parts by weight, the adhesiveness at low temperatures will be insufficient, which is not preferable. The polyisocyanate compound used in the present invention can be used regardless of whether it is aromatic, aliphatic, or araliphatic, as long as it has two or more NCO groups in one molecule.

Aromatic examples include tolylene diisocyanate, diphenylmethane-4,4-diisocyanate, and phenylene diisocyanate; aliphatic examples include hexamethylene diisocyanate, tetramethylene diisocyanate, and -dimethylcyclohexane diisocyanate. However, examples of the aromatic aliphatic type include 1.'-dimethylbenzene diisocyanate, and 2'-diethylbenzene diisocyanate. In the present invention, these polyisocyanates and low molecular weight polyol components are
An adduct having a terminal NCO obtained by an addition reaction such that the CO component is in excess can also be used. According to the polyolefin adhesive tape of the present invention, the carboxyl groups grown by activating the surface of the polyolefin foam react with the polyisocyanate compound blended in the mixture, and the surface of the foam reacts with the polyisocyanate compound blended in the mixture. The bond with the adhesive film becomes stronger, and as time passes, reactions with moisture, impurities, etc. in the adhesive composition also occur, and even when used to adhesively fix two hard articles, it has a good high performance. This provides retention properties.

Examples of the present invention are shown below.

The words "part of the text" indicate parts by weight. Example thickness 1. Then, corona discharge treatment was applied to both sides of a polyethylene foam sheet having a skin layer on the surface to prepare a sheet having a critical surface tension of 48 dyen'c.

On the other hand, styrene-butadiene-styrene block copolymer rubber 10 Togeto, terbene-based resin (softening point 115 qo)
A block copolymer rubber-based pressure-sensitive adhesive composition (apparent modulus of elasticity 1.8k9) consisting of 4 anchor parts, 8 loose parts of petroleum resin (softening point 85°C), 2 parts of a softener, and 3 parts of an anti-aging agent. To this, 3 or 5 parts of tolylene diisocyanate (B) is added to prepare a mixture or [B', respectively.

These mixtures were used to create a thickness of 0.05 on the template liner.
Create a willow adhesive film. This is laminated and pressed onto the surface of the polyethylene foam sheet to obtain the double-sided adhesive type polyolefin adhesive tape W or [B} of the present invention. Next, in order to evaluate the properties of this tape, measurements are made using the test method shown in the figure. That is, tape sample 2 (2 skins x 2 skins) was pasted between two BA finished stainless steel plates 1 and 1 in a side-itch pattern and crimped with a 2 kg braze, one of the stainless steel plates was fixed horizontally, and the other was A load W is applied to the end of the stainless steel plate, and the time until the load falls is measured (conditions: 25°C x 60% R.H.).

The results are shown in Table 1. In Table 1, Comparative Example 1 is obtained by forming the mixture (1) of Example into a polyethylene foam sheet which is not subjected to corona discharge treatment, and Comparative Example 2 is obtained by forming the mixture (1) of Example into a polyethylene foam sheet which is subjected to corona discharge treatment. It is coated with an adhesive composition that does not contain tolylene diisocyanate.

[Brief explanation of drawings]

The drawing is an explanatory diagram of the test method used to evaluate the adhesive tape of the present invention.

Claims (1)

[Claims] 1. At least one surface of the polyolefin foam is activated to have a critical surface tension of at least 41 dyne/cm, and the treated surface has an apparent elastic modulus of 0.9 to 20 kg. A polyolefin-based adhesive tape having an adhesive coating formed of a mixture of a block copolymer-based pressure-sensitive adhesive composition and a polyisocyanate compound having a diameter of /cm^2, which is firmly bonded. 2. The polyolefin adhesive tape according to claim 1, wherein the surface of the polyolefin foam is formed of a skin layer.