JPS629636B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to adhesive tapes or sheets based on foam. Conventionally, adhesive tapes based on rubber foams such as polychloroprene foam and butyl rubber foam have been used to fix the side moldings of automobiles, but rubber foams have insufficient flexibility.
If the fixed part has a step or a large curvature, it has a drawback that it is difficult to conform to the adherend and is easily peeled off. Adhesive tapes based on low-density polyethylene foam also have the disadvantage of having low mechanical strength and being easily destroyed by shearing force. In view of the above drawbacks, the object of the present invention is to provide a material that has high mechanical strength, excellent flexibility, and is suitable for applying shearing force to adherends with large irregularities or curvatures, such as fixing side moldings of automobiles. An object of the present invention is to provide an adhesive tape or sheet that can be stuck for a long period of time without being destroyed. That is, the gist of the present invention is an adhesive tape or an acrylic adhesive laminated on at least one surface of a flexible foam made of linear low-density polyethylene and an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer. Exists on the sheet. The linear low-density polyethylene used in the present invention is produced by, for example, ionic polymerization reaction under medium and low pressure to produce ethylene, propylene, butene-1, pentene-1, hexene-1, octene-1, 4-methylpentene-1, etc. of α-olefin (approximately 1
~10 mol%) copolymerization to introduce an appropriate number of short chain branches into the linear backbone polymer, thereby reducing the density to the range of ordinary high-pressure low-density polyethylene. 0.915~
0.94g/ ^cm3 , melt index 0.5~50g/10
It is preferable to have a melt index of 1.0 to 10.0 g/10 min. ) etc. The ethylene-vinyl acetate copolymer used in the present invention is a copolymer of ethylene and vinyl acetate, and one with a vinyl acetate content of 5 to 28% has good moldability, foam flexibility, adhesive properties, etc. It is preferable from the point of view. If the vinyl acetate content is too low, the adhesiveness and flexibility of the foam will be poor, and if it is too high, the moldability of the foam will be poor. The ethylene-ethyl acrylate copolymer used in the present invention is a copolymer of ethylene and ethyl acrylate, and those with an ethyl acrylate content of 7 to 25% have good moldability and flexibility of the foam. , is preferable from the viewpoint of adhesiveness and the like. If the content of ethyl acrylate is too small, the adhesiveness and flexibility of the foam will be poor, and if it is too large, the moldability of the foam will be poor. The foam used in the present invention is a soft foam made of the above-mentioned linear low-density polyethylene and an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer, and the expansion ratio is not particularly limited. However, it is preferably 3 to 20 times, more preferably 5 to 10 times. Moreover, the manufacturing method may be a conventionally known manufacturing method,
For example, a blowing agent is added to the above resin mixture, the mixture is uniformly mixed using a ribbon blender, etc., and the mixture is kneaded and melted using an extruder or calendar roll at a temperature and pressure that does not substantially decompose the blowing agent. A method of obtaining a crosslinked foam by forming the sheet into a sheet, crosslinking the sheet by irradiating the sheet with ionizing radiation, and then heating the foam to a temperature higher than the decomposition temperature of the blowing agent, or A mixture of a foaming agent and a crosslinking agent is mixed uniformly,
The foaming agent and crosslinking agent are kneaded and melted using an extruder or calender roll at a temperature and pressure that does not substantially decompose, formed into a sheet, and then crosslinked by heating this to a temperature at which the crosslinking agent decomposes. , and a method of obtaining a crosslinked foam by heating to a temperature higher than the decomposition temperature of the blowing agent. As the blowing agent, chemical blowing agents such as azodicarbonamide and N-N'-dinitrosopentamethylenetetramine, which generate decomposed gas when heated, are preferred because they do not require special equipment for use. When using ionizing radiation as a means of crosslinking resin, β rays, γ rays, neutrons, electron beams, etc. are used, and the irradiation dose is 0.5~
A range of 20 Mrad is preferred. In addition, when using a crosslinking agent as a means for crosslinking the resin, dicumyl peroxide, 2,5-dimethyl-2,5-
Organic peroxides such as ditertiary peroxyhexane and ditertiary butyl perterephthalate are used. The mixing ratio of linear low density polyethylene and ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer is in the range of 1:4 to 4:1 to improve the mechanical strength, flexibility, and It is preferable from the viewpoint of adhesiveness, moldability, etc. If the amount of linear low density polyethylene is too small, mechanical strength such as tensile strength will be insufficient, and if it is too large, flexibility and adhesiveness will be insufficient. Of course, in the above mixing, the ethylene-vinyl acetate copolymer and the ethylene-ethyl acrylate copolymer may be used together. In the present invention, the mixture further includes ordinary low density polyethylene, high density polyethylene,
It is also possible to add resins such as ethylene-propylene copolymer and polypropylene. For example, when adding ordinary low-density polyethylene, its density is 0.91 to 0.93 g/cm ³ and the melt index is 1 to 10.
g/10 min is preferred, and the total resin mixture
Up to 50% by weight can suitably be added. In addition, in producing the above foam, stabilizers,
Commonly used additives and auxiliaries such as ultraviolet absorbers, lubricants, pigments, antistatic agents, fillers, and reinforcing agents may be mixed. The adhesive tape or sheet of the present invention is formed by laminating an acrylic adhesive on at least one surface of the foam, and the acrylic adhesive has the general formula CH ₂ =CHCOOR (where R is 4 carbon atoms). A pressure-sensitive adhesive whose main component is a ^copolymer made of ^an acrylic ester represented by an alkyl group of . Examples of the acrylic ester include n-butyl acrylate, 2-ethylhexyl acrylate, isoamyl acrylate, n-octyl acrylate, etc., and the copolymer may be a (co)polymer of only acrylic ester. However, acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, N-methylolacrylamide, vinyl acetate, acrylonitrile, ethyl acrylate, methyl methacrylate, etc., which can be copolymerized with the above acrylic esters. It may also be copolymerized with monomers. Further, the weight average molecular weight of the copolymer is preferably 6×10 ⁵ to 10 ⁶ because as the molecular weight becomes smaller, the heat resistance creep property decreases, and on the other hand, as the molecular weight increases, the low temperature adhesiveness decreases. The above copolymer may be crosslinked with isocyanate, epoxy resin, metal salt, etc., and tackifiers, fillers, pigments, rust preventives, etc. may be added to the adhesive for the purpose of adjusting adhesive properties. Good too. Conventionally known production methods may be employed as the method for producing the above-mentioned pressure-sensitive adhesive, such as solution polymerization method, emulsion polymerization method, and the like. Furthermore, any conventionally known method may be used for laminating the adhesive on the foam, such as applying the adhesive to release paper, drying it, and then transferring it to the foam. Since the adhesive tape of the present invention has the above-mentioned structure, it has high mechanical strength and excellent flexibility, so it adapts well to uneven surfaces and surfaces with large curvature.
It can be stuck for a long time without breaking even when shearing force is applied, and can be suitably used for fixing the side moldings of automobiles. Also, the weight average molecular weight of the acrylic adhesive is 6×
If it is 10 ⁵ to 10 ⁶ , it has excellent heat-resistant creep and low-temperature adhesion, can be applied at low temperatures, and will not peel off even if exposed to high temperatures for a long time after adhesion. Next, the present invention will be explained with reference to examples. The physical properties were measured as follows. (1) Tensile strength: Compliant with JISK6767 (5.2 Tensile strength and elongation A method). (2) Compression hardness: Compliant with JISK6767 (5.3 Compression hardness). (3) Shear strength...Semi-rigid vinyl chloride resin plate (width 42 mm, length
100 mm) and double-sided adhesive tape (width 25 mm) for the sample.
25mm in length), crimped with a 5Kg rubber roll back and forth once, and left for 24 hours. Next, attach a melamine-coated steel plate to the other side of the double-sided adhesive tape, press it with a 5 kg rubber roll once, and leave it for 24 hours.
The tensile strength at break was measured at a speed of 50 mm/min. (4) Effective adhesion area...In standard conditions, a double-sided adhesive tape (width 25 mm, length 42 mm) of the sample was attached to approximately the center in the width direction of a semi-rigid vinyl chloride resin plate (width 42 mm, length 100 mm). Press a 5Kg rubber roll back and forth once and leave it for 24 hours. Next, on both sides, the thickness is 25 μm and the width is 8 mm.
Glue an aluminum plate with a length of 100mm,
A vinyl chloride resin board with the double-sided adhesive tape attached above was pasted on a transparent acrylic board with grooves 25 mm wide, and after being crimped with a 10 kg roll back and forth, the adhesive was stuck to the acrylic board. The area of the adhesive was measured, and the ratio of the adhesive area was taken as the effective adhesive area. (5) Low-temperature adhesion strength...In standard conditions, a semi-rigid vinyl chloride resin plate (width 42 mm, length 100 mm) is affixed with double-sided adhesive tape (width 25 mm, length 100 mm) to the length of the sample, and a 5 kg rubber roll is attached. Crimp it by going back and forth once and leave it for 24 hours. Next, it was pasted on a melamine-coated steel plate that was left in a constant temperature room at 5℃ for 3 hours, and was crimped with a 5Kg rubber roll once.
The splitting strength was measured at a speed of min. (6) Heat-resistant creep: A three-layer measurement sample was prepared in the same manner as the one used to measure shear strength, and a constant temperature room at 80°C was provided and the sample was suspended.
After 1 hour, a weight of 1 kg was suspended from the melamine-coated steel plate, and after 2 hours, the distance by which the adhesive tape had shifted was measured. Example 1 Density 0.918g/cm ³ , Melt index 2.0g/
30 parts by weight of 10-minute linear low-density polyethylene, vinyl acetate content 18%, melt index 2.5 g/
70 parts by weight of a 10-minute ethylene-vinyl acetate copolymer, 5 parts by weight of a blowing agent (azodicarbonamide), and 5.5 parts by weight of an auxiliary agent were mixed and extruded into a sheet using an extruder. With ray irradiation machine
Cross-linked by irradiating with 2.5 Mrad electron beam, then 250℃
The foamed sheet was heated and foamed by continuously passing it through an oven to obtain a foamed sheet with a thickness of about 1 mm. The resulting foamed sheet was flexible and had uniformly dispersed closed cells. The expansion ratio was 7 times. 70 parts by weight of a blend consisting of 90 parts by weight of 2-ethylhexyl acrylate, 9 parts by weight of acrylic acid, 1 part by weight of 2-hydroxyethyl methacrylate, 100 parts by weight of ethyl acetate and 0.02 parts by weight of azobisisobutylnitrile.
Polymerization was carried out at .degree. C. for 8 hours to obtain a pressure-sensitive adhesive composition with a solid content of 48%. The weight average molecular weight of the adhesive was 650,000 (gel permeation chromatography method). Add isocyanate (Japan Polyurethane Co., Ltd., Coronate L, solid content 55 parts by weight to 100 parts by weight of the above adhesive composition).
%) 4.4 parts by weight added and siliconized thickness 25
Coated on μm polyester film and dried to achieve thickness
A pressure-sensitive adhesive sheet having a 75 μm adhesive layer formed thereon was obtained. After corona discharge treatment was applied to both sides of the foamed sheet, the adhesive layer was transferred from the adhesive sheet to obtain a double-sided adhesive sheet. Using the obtained double-sided pressure-sensitive adhesive sheet, the physical properties (tensile strength, compressive hardness, shear strength, effective adhesive area, low-temperature adhesive strength, and heat-resistant creep) were measured, and the results are shown in Table 1. Example 2 30 parts by weight of the same linear low density polyethylene as in Example 1, 70 parts by weight of an ethylene-ethyl acrylate copolymer with an ethyl acrylate content of 18% and a melt index of 6 g/10 min, and a blowing agent 5 Parts by weight and auxiliaries
5.5 parts by weight, press-molded into a sheet,
Thereafter, it was crosslinked by irradiation with an electron beam of 2.5 Mrad, and then heated and foamed at 250°C to obtain a foamed sheet with a thickness of about 1 mm. The resulting crosslinked foam sheet had flexibility and uniformly dispersed closed cells. The foaming ratio was 6.3 times. The adhesive used in Example 1 was transferred onto the foamed sheet in the same manner as in Example 1 to obtain a double-sided adhesive sheet, and the physical properties were measured in the same manner and the results were reported as
Shown in the table. Example 3 30 parts by weight of the same linear low density polyethylene as in Example 1, 50 parts by weight of the same ethylene-vinyl acetate copolymer as in Example 1, density 0.923 g/cm ³ , melt index 4.0 g/10 min. 20 parts by weight of low-density polyethylene, 5 parts by weight of a foaming agent, and 5.5 parts by weight of an auxiliary agent were mixed, extruded into a sheet, and then
Cross-linked by irradiating with 2.5 Mrad electron beam, then 250℃
The mixture was heated and foamed to obtain a foamed sheet with a thickness of approximately 1 mm. The resulting crosslinked foam sheet had flexibility and uniformly dispersed closed cells. The foaming ratio is
It was 7.8 times higher. The adhesive used in Example 1 was transferred onto the foamed sheet in the same manner as in Example 1 to obtain a double-sided adhesive sheet, and the physical properties were measured in the same manner and the results were reported as
Shown in the table. Comparative Example 1 The resin was the same low density polyethylene 100 as in Example 3.
A foamed sheet with a thickness of about 1 mm was obtained in the same manner as in Example 3, except that only the parts by weight were changed. The foaming ratio was 7.5 times. The adhesive used in Example 1 was transferred to the foamed sheet in the same manner as in Example 1 to obtain a double-sided adhesive sheet, and the physical properties were measured in the same manner and the results are shown in Table 1. Comparative example 2 Chloroprene foam sheet with a thickness of 1 mm (foaming ratio
The adhesive used in Example 1 was transferred onto both sides of the sheet (2.0 times) in the same manner as in Example 1 to obtain a double-sided adhesive sheet, and the physical properties were measured in the same manner and the results are shown in Table 1.

[Table] * Foam sheet destroyed, all others destroyed at interface

Claims (1)

[Claims] 1. An adhesive tape comprising an acrylic adhesive laminated on at least one surface of a flexible foam made of linear low-density polyethylene and an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer. Or a sheet. 2. The adhesive according to claim 1, wherein the mixing ratio of linear low density polyethylene and ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer is in the range of 1:4 to 4:1. tape or sheet. 3 The acrylic adhesive has the general formula CH ₂ =
Patent for an adhesive mainly consisting of a copolymer consisting of an acrylic ester represented by CHCOOR (wherein R is an alkyl group having 4 to 8 carbon atoms) and having a weight average molecular weight of 6 x 10 ⁵ to 10 ⁶ An adhesive tape or sheet according to claim 1 or 2.