JPS6343436B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pressure-sensitive adhesive characterized in that when a tape or sheet coated with the pressure-sensitive adhesive is peeled off from an adherend, the peel strength decreases as the peel speed increases. When peeling an adhesive tape attached to a weak adherend such as a thin polyethylene or polypropylene film, sheet, or nonwoven fabric from the adherend, it is difficult to remove it without damaging the adherend. do not have. Furthermore, when the adhesive tape is unintentionally peeled off, the peeling speed is high, and adherends with weak material strength are inevitably damaged. This is a phenomenon that arises from the fact that in conventional adhesive tapes, as the peeling speed increases, the force required for peeling, that is, the peel strength increases. One possible way to avoid damage to the adherend during peeling is to reduce the peel strength of the adhesive tape as a whole. However, with adhesive tapes that have the property of increasing peel strength as the peeling speed increases, in order to prevent the adherend from tearing even if the adhesive tape is unintentionally peeled off from the adherend, it is necessary to The adhesive strength of the tape must be extremely low, and the disadvantage is that the adhesive tape does not adhere sufficiently to the adherend, or even if it does adhere, it peels off immediately, making it impossible to put it to practical use. The inventors of the present invention have made intensive studies to overcome the drawbacks of the conventional adhesive tapes described above, and as a result, they have invented an adhesive that has a characteristic that the peel strength is high when peeled at low speeds, and the peel strength is low when peeled at high speeds. be. That is, the present invention is a composition comprising 220 to 570 parts by weight of a terpene phenol resin and 40 to 130 parts by weight of a liquid rubber based on 100 parts by weight of a rubber elastomer. The present invention provides an adhesive characterized by having a property of decreasing strength. In this specification, the peeling speed means the moving speed of the edge of the adhesive tape to be peeled off. Therefore, when peeling is performed using a constant speed tensile tester, the peeling speed is the tensile speed. The decrease in peel strength due to an increase in peel speed as seen in the adhesive of the present invention does not occur discontinuously or suddenly at a certain peel speed, but as shown in the following examples, the peel strength decreases as the peel speed increases.
While increasing from 300mm/min to 4000mm/min,
The peel strength continuously decreases in the range of 10 to 50% based on the value at 300 mm/min. The adhesive tape or sheet coated with the adhesive of the present invention exhibits sufficient adhesive strength when used by pressing it onto an adherend, but the peel strength decreases when peeled off at high speed. Even adherends with weak strength in the relative relationship between adherend strength and peel strength do not break, and both the adherend and the adhesive tape or sheet can be reused. In this way, the adhesive tape or sheet coated with the adhesive of the present invention can be applied multiple times not only to strong adherends, but also to adherends whose strength is relatively weak relative to the peeling force. It can repeat adhesion and peeling over a period of time, and is indispensable in the development of products that require such operations. In addition, if the adhesive of the present invention is used when unwinding the adhesive tape wound into a roll in the manufacturing and processing process of adhesive tape, the unwinding speed can be increased because the peeling resistance is low even when unwinding at high speed. can. Furthermore, the adhesive tape can be easily rewound by simplifying the back surface treatment of the adhesive tape or by not performing any rear surface treatment. The rubber elastomer used in the present invention refers to a polymer compound that exhibits rubber elasticity at room temperature, and specific examples of the rubber elastomer include natural rubber, modified natural rubber, recycled rubber, polyisoprene rubber, neoprene rubber, Examples include chloroprene rubber, butadiene rubber, and isobutylene rubber. Further, the terpene phenol resin used in the present invention is a resin obtained by copolymerizing various phenols with various terpenes. Furthermore, the liquid rubber used in the present invention is a synthetic rubber with a relatively low molecular weight that exhibits viscous fluidity at room temperature, such as liquid polyisoprene rubber, liquid polybutadiene rubber, liquid (butadiene-styrene) copolymer, liquid Examples include (butadiene-acrylonitrile) copolymer, liquid polybutylene, and the like. More specifically, terpene phenol resin is a copolymer of phenols and terpenes such as α-pinene and β-pinene, and is estimated to have a structure as shown in the following formula. Commercially available products include YS Polyster manufactured by Yasushi Oil Industries Co., Ltd., which is used as a tackifier (tackifier) for rubber adhesives, and has properties such as improving tackiness and adhesion, and imparting anti-aging properties. It is said to be effective. A known manufacturing method is to heat terpenes and phenols in a solvent such as toluene in the presence of an acid catalyst (e.g., boron trifluoride, boron trifluoride etherate, etc.) to a temperature of usually 50 to 80°C. ing. The present invention has achieved a previously unknown special effect by incorporating a specific amount of terpene phenol resin into an adhesive based on a rubber elastomer, that is, the faster the peeling speed, the lower the peel strength. What I discovered is the beginning of this. That is, in the present invention, the purpose and effect of adding the terpene phenol resin is to impart tackiness and to adjust the dependence of peel strength on peel speed, as with conventional tackifiers. The two points are to make it small. On the other hand, in general pressure-sensitive adhesives, there is a relationship between peeling speed and peeling strength such that the faster the peeling speed, the higher the peeling strength. According to the present invention, in an adhesive containing a specific amount of terpene phenol resin, the mechanism by which the peel strength decreases as the peel speed increases is not clear, but
This seems to be related to the fact that the terpene phenol resin has a higher softening point than conventional tackifiers and has appropriate compatibility with the rubber component. The adhesive in the present invention is one in which the above-mentioned elastomer contains a terpene phenol resin and a liquid rubber, and one or two of the above-mentioned elastomers are used.
The above types, terpene phenol resin, and liquid rubber may be dissolved in a solvent and contained in a solution state, or they may be contained in a molten state by heating without using a solvent. Further, the terpene phenol resin and the liquid rubber can each be contained in the form of an emulsion in the elastomer latex or emulsion. Furthermore, the elastomer, terpene phenol resin, and liquid rubber may be mixed and then emulsified. The composition may further contain a latex or emulsion of other elastomers and/or tackifier resins to balance the adhesive properties. The content of terpene phenol resin in the adhesive of the present invention is 220 to 570 parts by weight, preferably 450 to 570 parts by weight, based on 100 parts by weight of the rubber elastomer, and the content of liquid rubber is 40 to 130 parts by weight. If the amount is outside this range, the peel strength will increase as the peel speed increases, or it will not be possible to obtain sufficient adhesive force required for adhesive tapes. In addition to the rubber elastomer, terpene phenol resin, and liquid rubber, other tackifier resins can be used in combination with the adhesive of the present invention, if necessary. In addition, rubber anti-aging agents, fillers, plasticizers, colorants, and when the adhesive is produced from an emulsion, various water-soluble polymers may be added as thickeners. Next, the present invention will be explained in further detail by showing examples and comparative examples of the present invention. Examples 1 to 3 and Reference Example 1 Latex of high molecular weight polyisoprene rubber with a number average molecular weight of 770,000 (trade name Maxprene IR-
900, manufactured by Seitetsu Kagaku Kogyo Co., Ltd.), liquid polyisoprene rubber latex with a viscosity average molecular weight of 30,000 (trade name: Claprene LIR-700, Clareisoprene Chemical)
Co., Ltd.), and the softening temperature measured by the ring and ball method is
An emulsion-type adhesive containing a 130°C terpene phenol resin emulsion (trade name Staron #2130, manufactured by Yasushi Oil Industries Co., Ltd.) in the solid weight parts shown in Table 1 is corona discharge treated and has a thickness of 170μ.
After applying it to a polyethylene film of 1 inch (2.54
cm) width to make adhesive tape. The thickness of the adhesive layer of this adhesive tape was approximately 40μ. The adhesive tape was cut into 125mm long and 30mm wide pieces with a thickness of 3mm.
500 on an embossed polyethylene sheet (thickness 30μ) pre-attached to an acrylic board with double-sided tape.
It was crimped with a roller of g. Then, manually peel off one end of the adhesive tape by approximately 25 mm, fix the acrylic plate and polyethylene sheet adherend from which the adhesive tape has been removed to the top chuck of a constant speed tensile tester, and attach the peeled adhesive tape to the bottom chuck at a 180° angle. The 180 degree peel strength was measured by a 180 degree angle constant speed peel adhesion test method in which the sheet was folded and fixed and a tensile test was performed at a constant speed. This method is based on the 180 degree peel adhesion measurement method specified in JIS C2107, but the width of the adhesive tape is 1 inch and the tensile speed is 300 degrees.
mm/min, 1000mm/min and 4000mm/min. All crimping operations and peel tests were conducted at 25°C.
A peel test was performed 30 minutes after the pressure bonding. As shown in Table 1, the peel strength decreased as the peel speed increased, and the 30 μm thick polyethylene sheet used as the adherend did not tear.

【table】

[Table] The peel strength retention rate shown in Table 1 is the ratio of the peel strength at a peel speed of 4000 mm/min to the peel strength at a peel speed of 300 mm/min, expressed as a percentage. Comparative Example 1 A latex of high molecular weight polyisoprene rubber with a number average molecular weight of 770,000, a latex of liquid polyisoprene rubber with a viscosity average molecular weight of 30,000, and a softening temperature of 130 as measured by the ring and ball method in the same manner as in Example 1.
The relationship between peeling speed and 180 degree peel strength was measured for emulsion-type adhesives containing 100 parts by weight, 11 parts by weight, and 30 parts by weight of terpene phenol resin emulsions, respectively, in terms of solid content.
As shown below, as the peel rate increased, the peel strength also increased.

[Table] From Reference Example 1 and Comparative Example 1, the content of terpene phenol resin per 100 parts by weight of elastomer is approximately
It can be seen that when the content is less than 40 parts by weight, the peel strength increases as the peel rate increases, but when the content exceeds this value, the peel strength decreases. Furthermore, from the results of Examples 1 to 3, when 220 to 570 parts by weight of terpene phenol resin and 40 to 130 parts by weight of liquid rubber were blended to 100 parts by weight of the elastomer according to the present invention, the peel strength decreased due to the increase in peel speed. It can be seen that this occurs significantly (peel strength retention rate: 10-50%). Comparative Examples 2 and 3 An emulsion mold in which a latex of high molecular weight polyisoprene rubber with a number average molecular weight of 770,000 and an emulsion of a terpene phenol resin with a softening temperature of 130°C measured by the ring and ball method were blended in the solids weight parts shown in Table 2. 180% for the adhesive in the same manner as in Example 1.
A peel test was conducted.

【table】

[Table] As shown in Comparative Example 2, when no liquid rubber is included, the peel strength is low overall, and the peel strength increases as the peel speed increases. Comparative Example 3 is an example in which no liquid rubber was contained and the content of terpene phenol resin was high, and in this case, the adhesive strength was 0. Comparative Example 4 In the same manner as in Example 1, a latex of high molecular weight polyisoprene rubber with a number average molecular weight of 770,000, a latex of liquid polyisoprene rubber with a viscosity average molecular weight of 30,000, and a softening temperature measured by the ring and ball method of 130°C.
The relationship between peeling speed and 180 degree peel strength was measured for emulsion-type adhesives containing 100 parts by weight, 160 parts by weight, and 116 parts by weight of terpene phenol resin emulsions, respectively, in terms of solid content, as shown below. There was a tendency for the 180 degree peel strength to increase as the peel speed increased, and the adherend broke at 4000 mm/min. If the amount of the liquid rubber component is too large as described above, the characteristics of the present invention will be lost.

【table】

Claims (1)

[Scope of Claims] 1. An adhesive composition comprising 220 to 570 parts by weight of a terpene phenol resin and 40 to 130 parts by weight of liquid rubber based on 100 parts by weight of a rubber elastomer. 2. The adhesive composition according to claim 1, wherein the rubber elastomer is natural rubber or polyisoprene rubber. 3. The adhesive composition according to claim 1 or 2, wherein the liquid rubber is liquid polyisoprene rubber.