JPS599589B2 - Primer composition for adhesive sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a primer composition for an adhesive sheet or tape having a propylene homopolymer film and a polyolefin plastic film containing a propylene component as a support.

Conventionally, in adhesive sheets for surface protection of various adhesive tapes, metal plates, resin plates, plywood, etc., in order to obtain sufficient bonding strength between the base film and the adhesive, the film surface is physically or chemically oxidized or corona-treated. Efforts have been made to apply corona treatment using electrical discharge and undercoat treatment using polyurethane compounds.

However, all of these treatment methods are aimed at activating the surface of polyolefin films, which have poor chemical activity, and adhesives that can obtain good bonding strength with such treated surfaces include various polymeric acrylic esters. There are known pressure-sensitive adhesives containing vinyl ether polymers as main components, and these types of adhesive sheets for surface protection are currently on the market, but they have the following drawbacks. In other words, since the above-mentioned adhesive is chemically active and reactive, it may contaminate the surface of the adherend, which is highly susceptible to change, or the adhesive may remain after the protective sheet is used. This causes problems such as the protective sheet becoming unable to be peeled off.

On the other hand, pressure-sensitive adhesives mainly made of polyisobutylene rubber are extremely chemically inert and non-reactive due to their molecular structure, so they do not contaminate the surface of the adherend or leave any adhesive residue. , etc., although the properties useful as adhesives for protective sheets are protected, the film cannot be used properly without modification for the purpose of activating the adhesive. It has no strong binding force. Therefore, it is difficult to create an adhesive sheet that has sufficient bonding strength between the adhesive and the base film by combining an adhesive mainly composed of polyisobutylene rubber and a polyolefin film, especially a propylene homopolymer film. However, a satisfactory primer that can provide such a pressure-sensitive adhesive sheet is not yet known. As described above, the present inventors have developed various types of primers in order to provide a primer suitable for use in adhesive sheets, which is a combination of an adhesive mainly composed of polyisobutylene rubber and a polyolefin film, which is useful as an adhesive for protective adhesive sheets. As a result of intensive experiments and research, we have found that a propylene homopolymer film as a base film, a polyolefin film containing 5% or more of polypropylene as a component, and an adhesive mainly composed of polyisobutylene rubber, butyl rubber, or a mixture of both. As an undercoat that can provide strong bonding strength between the It was concluded that a mixture containing 20 to 95 parts of one or two of these is extremely effective, leading to the completion of the present invention.

Here, to estimate the strong bonding force between the base film and adhesive when the above-mentioned primer is used, the bonding strength between the propylene component in the base film and the chlorinated polypropylene in the primer, and the adhesive This is thought to be due to the bonding effect between the non-polar rubbers of the polyisobutylene rubber and butyl rubber in the primer and the polyisobutylene rubber and butyl rubber in the primer. The chlorinated polypropylene and the non-polar amorphous rubber material have good compatibility, and even after the primer coat is applied and dries, the intertwined state of the different molecules remains stable. It is believed that the primer in the invention exhibits this effect.

In general, the good bonding strength between chlorinated polypropylene and polypropylene film is well-known, but applying chlorinated polypropylene to polypropylene film gives polarity to the surface of the film, which lacks polarity, to improve sealing properties and improve the bonding strength of other films. An example of use as an adhesive for lamination with a polyolefin film or as a paint binder to obtain bonding strength between an extremely chemically inert adhesive as in the present invention and a polyolefin film with poor polarity. There is no. In particular, the present invention makes it possible to use a homopolymerized propylene film, whether stretched or unstretched, as a base film for the adhesive mainly composed of the above-mentioned non-polar amorphous rubber, and to make it into a pressure-sensitive adhesive sheet. This is something worth noting.

In Japanese Patent Publication No. 50-14667, it is assumed that propylene homopolymers cannot have good affinity with adhesives made of amorphous rubber because the resin has a highly regular arrangement. Judging from the fact that it has been suggested that it would be difficult to realize a pressure-sensitive adhesive sheet by combining the two, the effectiveness of the present invention is clear.

The primer of the present invention is particularly effective for propylene homopolymer films, but is also effective for polyolefin films containing 5% or more of polypropylene, in which case, in addition to polypropylene, polyethylene or ethylene monovinyl acetate copolymer, etc. A polyolefin or an olefin-based copolymer or mixture is added.

As polypropylene, any of propylene homopolymers, copolymers, and blends can be used. Now, regarding the composition of the primer in the present invention, the chlorine content of the chlorinated polypropylene is 15 to 40%, preferably 20 to 3
0%, which means that if the chlorine content is less than 15%, the solubility in solvents will be insufficient and workability will be extremely poor.
This is because if it exceeds 40%, the bonding strength with the base film will be insufficient.

In addition, the content of chlorinated polypropylene in the primer is 5 to 5.
80 parts, preferably 10 to 70 parts, because if it is less than this, sufficient bonding strength between the primer and the base film cannot be obtained, and if it is more than this, good affinity will be obtained between the adhesive and the primer. This is because it cannot be obtained. Accordingly, 20 to 95 parts of one or both of polyisobutylene rubber and butyl rubber are used. The undercoat is used by dissolving these components in an organic solvent such as benzene, toluene, xylene, n-hexane or the like at a ratio of about 0.1 to 15%. Toluene is preferable in terms of price. In addition to this, polybutene, rosin or its derivatives, terpene resin, phenolic resin, pine oil, etc. can be added as an appropriate adhesion agent, if necessary. Therefore, this primer requires both chlorinated polypropylene and one or both of polyisobutylene rubber and butyl rubber; chlorinated polypropylene alone is not effective at all, and in fact, when there is no top or bottom coating, The same is true; on the other hand, using only polyisobutylene rubber or butyl rubber corresponds to using no primer and is similarly ineffective.

As mentioned above, the adhesive suitable for use with this primer is mainly composed of non-polar amorphous rubber, and those mainly composed of polyisobutylene rubber are preferably used.

Polyisobutylene rubber-based materials can be used in various forms, such as isobutylene polymers, random copolymers of isobutylene and normal butylene, copolymers of isobutylene and isoprene, or vulcanized products thereof. These are usually used as organic solvents such as benzene, toluene, xylene, n-hexane, etc., and can adhere well to the primer without using a tackifier as mentioned above. It can also be used. As the chlorinated polypropylene used in the present invention, the trade name "Hardren" manufactured by Toyo Kasei Kogyo Co., Ltd. is known. Depending on the molecular structure of the base polypropylene, there are chlorinated isotactic polypropylene and chlorinated atactic polypropylene, each depending on the chlorine content. There are various types, and any of them can be used. As a polyisobutylene rubber, the product name "VISTANEX" manufactured by Etsuo Co., Ltd. is known, and it has a molecular weight of 10,000 to 1.
40,000 and Etsuso's "Etsubutyl" are known, and have an unsaturation degree of 0.5 to 3 (mol%) and a viscosity of 60.
The following materials that are hard to age and non-staining can be used.

Examples will be described below, but the present invention is not limited by the examples.

The thickness of the adhesive made from Example 1 after drying is 0.01 m! It was coated and dried to form an adhesive sheet.

The properties of this adhesive sheet are shown in Table 1. Example 2 A primer and adhesive were applied to one side of a stretched polypropylene film with a thickness of 0.05 mm in the same manner as in Example 1, and dried.
It was made into an adhesive sheet.

The properties of this adhesive sheet are shown in Table 1. Example 3 A primer and adhesive were coated on one side of a 0.05 mm thick melt-extruded film made of 20 parts of polyethylene and 80 parts of polypropylene, and dried in the same manner as in Example 1 to obtain a pressure-sensitive adhesive sheet.

The properties of this adhesive sheet are shown in Table 1. Comparative Example 1 The adhesive of Example 1 was applied to one side of an unstretched polypropylene film with a thickness of 0.05 m1, and the thickness after drying was 0.01 mm1.
The mixture was coated and dried to form an adhesive sheet.

The properties of this adhesive sheet are shown in Table 1. Comparative Example 2 The adhesive of Example 1 was applied to one side of a melt-extruded film made of 20 parts of polyethylene and 80 parts of polypropylene and had a thickness of 0.0511 mm so that the thickness after drying was 0.01 mm. It was dried and became adhesive. It was made into a sheet.

The properties of this adhesive sheet are shown in Table 1. Comparative example 3 Thickness 0.05W! A toluene solution of chlorinated polypropylene (Hardlene 13LP, manufactured by Toyo Kasei Co., Ltd.) was applied as a primer to one side of a 1.1 unstretched polypropylene film, and the thickness after drying was 0.002 V1. Apply and dry so that
The adhesive of Example 1 was applied on top of it to a thickness of 0.011 after drying.
It was coated and dried in an area of 1 m to form a pressure-sensitive adhesive sheet.

The properties of this adhesive sheet are shown in Table 1. As shown in Table 1, Comparative Example 1 without using the primer composition according to the present invention
It is clear that the bonding strength with the base material, weather resistance, staining resistance (heat resistance), and evaluation in the cases of 3 to 3 are markedly lower than those of the examples of the present invention.

Claims (1)

[Claims] 1. An undercoat composition for pressure-sensitive adhesive sheets, comprising chlorinated polypropylene having a chlorine content of 15 to 40% (wt%) and one or two of polyisobutylene rubber and butyl rubber.