JP3290261B2 - Pressure-sensitive adhesive composition for surface protective material and surface protective material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a surface protection sheet or tape (hereinafter referred to as a surface protection material) for a painted plate, a metal plate, a resin plate, etc. The present invention relates to a pressure-sensitive adhesive composition for a surface protective material having very small change over time in adhesive strength after bonding and having practical weather resistance, and a surface protective material using the same.

[0002]

2. Description of the Related Art Conventionally, acrylic adhesives and rubber adhesives mainly composed of rubber such as natural rubber and polyisobutylene have been used as adhesives used for surface protective materials such as painted plates, metal plates and resin plates. It is widely used and partially uses ethylene-vinyl acetate copolymer (EVA), styrene / butadiene / styrene block copolymer (SBS), and styrene / isoprene / styrene block copolymer (SIS) adhesives. ing. However, these have the following problems.

(1) Since the acrylic adhesive itself has a high polarity, the adhesive strength after application of the surface protective material is extremely large, and when the surface protective material is peeled off from the adherend, the peel strength is large. Workability is extremely poor, and in extreme cases, glue remains on the adherend surface. (2) Polyisobutylene and block copolymer adhesives have a small increase in adhesive strength as compared with acrylic adhesives, but are not at a level that facilitates the peeling operation. (3) Natural rubber-based, EVA-based, SIS-based, and SBS-based adhesives easily deteriorate in a short time due to sunlight or the like. There is a problem of weather resistance that residue tends to occur. (4) The EVA-based adhesive is a heat-adhesive type, and if the surface of the adherend has some irregularities, good initial adhesive strength cannot be obtained with pressure sensitivity.

[0004] In order to improve the above (1) and (2), there has been known an adhesive obtained by adding various surfactants to an adhesive. Since such a surfactant exerts its effect when present at the interface with the adherend, it is effective when the adherend is a metal plate. However, when the adherend is a painted plate coated with paint, the molecular weight of these surfactants is as small as several tens to several hundreds. Occur. As a result, since the surfactant does not exist at the interface, there is a problem that there is no sustainability for suppressing an increase in the adhesive force. Further, when a surfactant is added to a low-polarity rubber-based adhesive, there is a problem that the surface of the adherend is easily contaminated due to poor compatibility.

As an improvement of the above (3), addition of various anti-aging agents, ultraviolet absorbers and the like has been studied, but the properties of the surface protective material are insufficient. Further, as an improvement measure of the above (4), an adhesive is softened by adding a tackifier, a process oil or the like in a larger amount, but the cohesive force is reduced and the adhesive tends to remain. However, there is a problem that the weather resistance is also reduced. In any case, it is the present situation that a material having sufficient characteristics has not been obtained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to have good adhesiveness at the time of laminating, and to have a very small change in adhesive force with time after laminating, and to have practical weather resistance. An object of the present invention is to provide a pressure-sensitive adhesive composition for a surface protective material and a surface protective material.

[0007]

SUMMARY OF THE INVENTION The present invention has been developed to achieve the above object. That is, the present invention is a pressure-sensitive adhesive composition for a surface protective material comprising 100 parts by weight of a polymer having an isobutylene unit as a main component and 3 to 20 parts by weight of a wax having an acid value of 3 to 90. Further, it is a surface protective material having a layer made of the pressure-sensitive adhesive composition on a substrate.

The polymer having an isobutylene unit as a main component used in the adhesive composition of the present invention includes polyisobutylene, a random copolymer of isobutylene and normal butylene, a copolymer of isobutylene and isoprene (regular butyl rubber, chlorine Butyl rubber, brominated butyl rubber, partially cross-linked butyl rubber, etc.) or vulcanized or modified products thereof (modified with a functional group such as a hydroxyl group, a carboxyl group, an amino group, an epoxy group), and the like. Isobutylene, a random copolymer of isobutylene and normal butylene. Where "principal component"
Means that the proportion of isobutylene units in the whole polymer is 5
It is preferably at least 0% by weight, particularly preferably at least 80% by weight.

A polymer having an isobutylene unit as a main component has an appropriate viscoelasticity in a normal temperature range and has almost no unsaturated double bond in a molecule. Therefore, an adhesive composition using the polymer is used. Can have good initial adhesion and weather resistance.

The wax used in the adhesive composition of the present invention may be liquid or solid, and specific examples thereof include low molecular weight polyethylene wax and low molecular weight polypropylene wax which are synthetic waxes. Preferably, it is a low molecular weight polyethylene wax.

In the present invention, the wax must have an acid value of 3 to 90 (KOH mg / g, JIS K5902), preferably 10 to 70. Therefore, an oxidized wax obtained by graft polymerization of dicarboxylic acid, acrylic acid, maleic acid, or the like to the above wax or by heating and oxidizing in the presence of oxygen is used.

When the acid value is less than 3, the polar group in the wax is small, so that the adsorbability and affinity of the wax to the adherend are reduced. The effect of suppressing an increase in force cannot be obtained. If the acid value is more than 90, the adsorbability and affinity for the adherend are too large, so that the wax is too much at the interface to lower the initial adhesiveness, and good laminating properties cannot be obtained.

Further, the adhesive composition needs to contain 3 to 30 parts by weight of the oxidized wax with respect to 100 parts by weight of the polymer having the isobutylene unit as a main component, and 3 to 20 parts by weight. It is preferable to include them. If the added amount of the oxidized wax is less than 3 parts by weight, the effect of suppressing the increase in the adhesive force with the passage of time cannot be obtained. If the added amount exceeds 30 parts by weight, too much wax comes to the interface and the initial adhesiveness decreases, Good lamination properties cannot be obtained.

The molecular weight of these waxes is usually 1,00
0 to 10,000, and even if the adherend is a painted plate, the wax does not move from the adhesive composition into the paint of the adherend after application.

The oxidized wax is used to suppress an increase in adhesive force with the passage of time. However, when the oxidized wax is mixed with a polymer having an isobutylene unit as a main component,
The effect appears best.

In the adhesive composition of the present invention, depending on the purpose, various materials such as antioxidants and ultraviolet absorbers which are commonly used may be used within a range not inconsistent with the gist of the present invention.

Furthermore, a surface protective material can be prepared by forming the above-mentioned adhesive composition as an adhesive layer on the following base material.

As the substrate of the surface protective material, conventionally known ones are used, and examples thereof include polyolefin-based films and the like, and preferred are polypropylene-based films, polyethylene-based films, and films made of blends thereof. If necessary, these films may be subjected to an adhesive treatment (corona treatment, undercoating treatment, etc.) or a back surface treatment.

In the surface protective material, the thickness of the adhesive layer is preferably 1 to 200 μm, more preferably 1 to 5 μm.
0 μm, and the thickness of the substrate is preferably 5 to 300 μm.
m, more preferably 10 to 100 μm.

The surface protective material can be easily produced, for example, by dissolving the adhesive composition in an organic solvent and applying the solution on a substrate by a conventional method. Further, it can be easily produced by melt co-extrusion of a polyolefin resin or the like as a base material with an adhesive composition.

[0021]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. All parts in the text are by weight.

Examples 1-2, Comparative Examples 1-11 As a substrate, a 40 μm polypropylene / polyethylene blend film (composition ratio: 70 /
30), an adhesive composition having the composition shown in Table 1 was applied to the corona-treated surface using a roll coater so as to have a solid content (film thickness after drying) of 5 μm.
After drying for a minute, a surface protective material was prepared.

[0023]

[Table 1]

EXPERIMENTAL EXAMPLE 1 The above surface protective material was bonded to a melamine-based coated plate using a laminator (bonding pressure 70 N / cm, bonding speed 5 m / min), and the tests for adhesive strength and weather resistance were performed as follows. I went. Table 2 shows the results.

(1) Adhesive force 30 minutes after the application of the surface protective material, the adhesive force measured under the conditions of a peel angle of 180 ° and a pulling speed of 0.3 m / min was used as an initial value, and a 70 ° C. heating acceleration test was performed for 3 days (Arrhenius) (Equivalent to about one year at room temperature when converted by the formula) After that, the adhesive strength was measured in the same manner as above.

(2) Weather Resistance A sample was fixed outdoors and subjected to an outdoor exposure test. 10, 20, 30, and 90 days after the exposure, the surface protective material was peeled off, and the presence of adhesive residue and contamination at that time were examined. When no adhesive residue / contamination was observed, it was evaluated as ○, and when adhesive residue / contamination was observed, it was evaluated as x.

[0027]

[Table 2]

[0028]

According to the present invention, a surface protective material having good adhesiveness at the time of lamination, a very small change in the adhesive force after lamination with time, and practical weatherability is provided. A pressure-sensitive adhesive composition and a surface protective material can be provided, and their industrial value is great.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C09J 123/22 C09J 7/02

Claims (2)

(57) [Claims] 1. A wax having an acid value of 3 to 90 and a wax of 3 to 20 per 100 parts by weight of a polymer having an isobutylene unit as a main component.
A pressure-sensitive adhesive composition for a surface protective material, comprising parts by weight. 2. A surface protective material having a layer comprising the pressure-sensitive adhesive composition according to claim 1 on a substrate.