JP5242229B2 - Heat release type adhesive sheet - Google Patents

Description

The present invention relates to a heat-peelable pressure-sensitive adhesive sheet comprising a polyester-based polymer having a plant-derived material that is friendly to the global environment as an active ingredient.

After the heat-peelable pressure-sensitive adhesive sheet is used after being attached to an adherend, it is heat-peeled and discarded. So far, this type of pressure-sensitive adhesive sheet has mainly used an acrylic material derived from petroleum as a pressure-sensitive adhesive (Patent Document 1).
Japanese Patent Laid-Open No. 2005-17996

Since the conventional heat-peelable pressure-sensitive adhesive sheet is a petroleum-derived material, there is a risk of oil depletion, and carbon dioxide is discharged during disposal after use. In other words, no consideration was given to the global environment in terms of oil depletion and carbon dioxide emissions during industrial waste.

In recent years, environmental considerations have been demanded as a countermeasure against depletion of fossil resources and global warming, and the use of plant-derived materials, which are renewable materials, is recommended.

In light of such circumstances, the present invention uses, as an adhesive, a fossil resource (including petroleum resources), a plant-derived material that is friendly to the global environment and has no problems of fossil resource depletion or carbon dioxide emissions. It is an object to provide a heat-peelable pressure-sensitive adhesive sheet.

As a result of intensive studies on the above problems, the present inventors have made a polyester-based polymer made from a plant-derived material a raw material component as an active ingredient of a pressure-sensitive adhesive, and include a foaming agent in the pressure-sensitive adhesive layer that can be heated and foamed. By configuring it, when the gel fraction of this adhesive layer is set to an appropriate range by crosslinking, etc., it exhibits good adhesive force during use and can be easily peeled off by heating foam when discarded after use This waste material is known to be environmentally friendly and has no problem of carbon dioxide emission due to the plant-derived material, and the present invention has been completed.

That is, the present invention is, on at least one surface of a substrate, using a polyester-based polymer obtained by condensation polymerization of dimer diol is a diol dimer acid and plant-derived dicarboxylic acid derived from a plant, the gel fraction The adhesive layer has a rate of 40 to 85%, and the adhesive layer contains 5 to 60 parts by weight of a foaming agent composed of thermally expandable microspheres per 100 parts by weight of the polyester polymer. The present invention relates to a heat-peelable pressure-sensitive adhesive sheet characterized by having a force of 2 N / 20 mm or more and an adhesive force after heating and foaming (160 ° C., 1 minute) of 0.3 N / 20 mm or less .

As described above, in the present invention, the use of a polyester-based polymer made of plant-derived material as a raw material component as an effective component of the pressure-sensitive adhesive makes the pressure-sensitive adhesive sheet heat-peelable by using a foaming agent, thereby affecting the depletion of fossil resources. In addition, since a plant-derived material is used for disposal after use, a heat-peelable pressure-sensitive adhesive sheet that is friendly to the global environment and can realize carbon neutral even when carbon dioxide is discharged can be provided.

In addition, this heat-peelable pressure-sensitive adhesive sheet is used in the preparation of a pressure-sensitive adhesive containing the above-mentioned polymer as an active ingredient. Can be made into an O / D type gel emulsion, and water can be added to this gel emulsion to make an O / W type emulsion.], Thereby preventing VOC (Voratile Organic Compounds) It is also possible to contribute to the removal of organic solvents.

The polyester polymer in the present invention is obtained by condensation polymerization of these raw material components using plant-derived dicarboxylic acid and plant-derived diol as raw material components (monomer components). The weight average molecular weight (Mw) is usually from 50,000 to 150,000.

The above condensation polymerization may be performed by an ordinary method using an organic solvent, or may be performed without a solvent under reduced pressure. The dicarboxylic acid and the diol are preferably equimolar reaction, but in some cases, either of them may be reacted as a larger number of moles. In the reaction, an appropriate catalyst such as a metal compound such as tetra-n-butyl titanate, tetraisopropyl titanate, antimony trioxide, or butyltin oxide can be used.

The plant-derived dicarboxylic acid is not particularly limited as long as it is plant-derived, and examples thereof include dimer acid produced from castor oil-derived sebacic acid and oleic acid. Two or more of these dicarboxylic acids can be used in combination.

The plant-derived diol is not particularly limited as long as it is derived from a plant, and examples thereof include fatty acid esters derived from castor oil and dimer diols produced from oleic acid. Two or more kinds of such diols can be used in combination.

Aside from plant-derived dicarboxylic acids and plant-derived diols, non-plant-derived dicarboxylic acids and diols can also be used in combination. However, these non-plant-derived dicarboxylic acids and diols may be 30% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less, and most preferably 5% by weight or less of the total raw material components.

In the present invention, the above-mentioned polyester-based polymer is used as an active ingredient of the pressure-sensitive adhesive, and a foaming agent and usually a crosslinking agent are blended therein to prepare a pressure-sensitive adhesive.

The pressure-sensitive adhesive may be prepared using an organic solvent or in the absence of a solvent. Alternatively, an emulsion-type pressure-sensitive adhesive emulsified and dispersed in water may be used, and emulsification by D-phase emulsification may be used to facilitate emulsification and dispersion.

In the D phase emulsification, the above polymer is dispersed as an oil component in a surfactant phase (D phase) containing water and a polyhydric alcohol to form an O / D type gel emulsion. A W-type emulsion is used. A foaming agent and a crosslinking agent may be added together with the polymer, or may be blended after obtaining the emulsion. According to D-phase emulsification, VOC measures can be taken, which can contribute to the removal of organic solvent.

As the foaming agent, heat-expandable fine particles, particularly heat-expandable microspheres are preferably used. The heat-expandable microsphere can be appropriately selected from known heat-expandable microspheres, but a microencapsulated foaming agent is preferably used from the viewpoint of easy mixing operation.

Examples of such thermally expandable microspheres include microspheres in which substances such as isobutane, propane, and pentane that are easily gasified and expanded by heating are encapsulated in an elastic shell. The shell is often formed of a hot-melt material or a material that is destroyed by thermal expansion. Examples of the substance forming the shell include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone.

Thermally expandable microspheres can be produced by a conventional method such as a coacervation method or an interfacial polymerization method. For the thermally expandable microspheres, for example, a commercially available product such as “Matsumoto Microsphere” (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) may be used.

In order to reduce the adhesive force of the heat-expandable adhesive layer efficiently and stably by heat treatment, it does not burst until the volume expansion coefficient is 5 times or more, especially 7 times or more, especially 10 times or more. Thermally expandable microspheres having the following are preferred:

The particle diameter of the heat-expandable microsphere can be appropriately selected according to the thickness of the adhesive layer. The average particle diameter of the heat-expandable microspheres can be selected from the range of, for example, 100 μm or less, preferably 80 μm or less, more preferably 10-50 μm, and particularly 1-30 μm. The adjustment of the particle size of the thermally expandable microspheres may be performed in the process of generating the thermally expandable microspheres, or may be performed manually by classification or the like after the generation.

In the present invention, a foaming agent other than the thermally expandable microsphere can be used together with the above thermally expandable microsphere or in place of the thermally expandable microsphere.

As such a foaming agent, various foaming agents such as various inorganic foaming agents and organic foaming agents can be appropriately selected and used.

Typical examples of the inorganic foaming agent include ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, various azides and the like.

Representative examples of organic foaming agents include, for example, water; chlorofluorinated alkane compounds such as trichloromonofluoromethane and dichloromonofluoromethane; azobisisobutyronitrile, azodicarbonamide, barium azodicarboxylate Azo compounds such as paratoluenesulfonyl hydrazide, diphenylsulfone-3,3'-disulfonyl hydrazide, hydrazine compounds such as 4,4'-oxybis (benzenesulfonyl hydrazide), allyl bis (sulfonyl hydrazide); p-toluylene Semicarbazide compounds such as sulfonylresemicarbazide and 4,4'-oxybis (benzenesulfonyl semicarbazide); Triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole; N, N'-dinitrosopenta Terenteroramin, N, etc. N- nitroso compounds such as N'- dinitrosoterephthalamide, and the like.

The amount of the foaming agent is 5 to 60 parts by weight, preferably 5 to 40 parts by weight, and more preferably 5 to 15 parts by weight with respect to 100 parts by weight of the polyester polymer.

When the amount of the foaming agent is too large, not only the interface between the adherend and the adhesive layer is peeled but also peeling occurs between the substrate and the substrate when heated and foamed. On the other hand, if the amount of the foaming agent is too small, the adhesive force does not decrease even after heat foaming and cannot be easily peeled off from the adherend.

As the crosslinking agent, a polyfunctional compound capable of reacting with a functional group (carboxyl group, hydroxyl group, etc.) contained in the polyester polymer molecule to form a crosslinked structure of the polymer is used. Of these, polyisocyanate compounds are preferred.

Examples of the polyisocyanate compound include lower aliphatic polyisocyanates such as butylene isocyanate and hexamethylene diisocyanate, alicyclic polyisocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, 2,4-tolylene diisocyanate, 4 Aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate and xylerin diisocyanate; and isocyanate adducts such as tolylene diisocyanate adduct of trimeterolpropane and hexamethylene diisocyanate adduct. Two or more of these crosslinking agents may be used in combination.

Although the kind and compounding quantity of a crosslinking agent are arbitrary, it is preferable to mix | blend so that the gel fraction of an adhesion layer may be 40 to 85%, Preferably it is 50 to 75%.

If the gel fraction is too low, the adhesive strength is high even after heating and foaming, and peeling becomes difficult. On the other hand, if the gel fraction is too high, the initial adhesive strength is low, and peeling is likely to occur before heating.

In the present invention, the pressure-sensitive adhesive prepared as described above is applied onto a substrate and dried as necessary, thereby having a pressure-sensitive adhesive layer on at least one surface of the substrate, and a foaming agent in the pressure-sensitive adhesive layer. A heat-peelable pressure-sensitive adhesive sheet containing

The thickness of the pressure-sensitive adhesive layer can be appropriately set, but is usually 10 to 50 μm, preferably 20 to 40 μm. In addition, when this pressure-sensitive adhesive layer is heated and foamed, it may peel off between the pressure-sensitive adhesive layer and the base material layer. Therefore, if necessary, a foaming agent is included between the base material and the pressure-sensitive adhesive layer containing the foaming agent. Another adhesive layer that is not present may be provided.

Examples of the substrate include paper-based substrates such as paper; fiber-based substrates such as woven fabrics, nonwoven fabrics, felts, and nets; metal-based substrates such as metal foils and metal plates; plastics such as plastic films and sheets. Base materials: rubber base materials such as rubber sheets; foams such as foam sheets, and laminates thereof [particularly, laminates of plastic base materials and other base materials, and laminates of plastic films or sheets] An appropriate thin leaf body such as a body is used.

Among these, plastic base materials such as plastic films and sheets can be suitably used. Moreover, what is excellent in the heat resistance which does not melt at the heat processing temperature of an adhesion layer is preferable from points, such as the handleability after a heating.

Examples of the material for the plastic base material include olefin resins having α-olefin as a monomer component such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), and the like. Polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PET); polyvinyl chloride (PVC); polyphenylene sulfide (PPS); polyamide (nylon), wholly aromatic polyamide (aramid) Amide resins such as polyether ether ketone (PEEK). These materials can be used alone or in combination of two or more.

In addition, when using such a plastic-type base material, deformability, such as elongation rate, can be suitably controlled by an extending | stretching process etc.

The thickness of the substrate can be appropriately selected according to the strength, flexibility, purpose of use, and the like of the substrate. Generally, it is 1,000 μm or less (for example, 1 to 1,000 μm), preferably 1 to 500 μm, more preferably 3 to 300 μm, and particularly preferably about 5 to 250 μm, but is not limited thereto.

In order to improve the adhesion of the substrate surface to the adhesive layer formed on the substrate, conventional surface treatments such as chromic acid treatment, ozone exposure, flame exposure, high piezoelectric impact exposure, ionizing radiation treatment, etc. An oxidation treatment or the like by a physical or physical method may be performed, or a coating treatment with a primer may be performed.

The heat-peelable pressure-sensitive adhesive sheet of the present invention includes a foaming agent in the pressure-sensitive adhesive layer provided on at least one surface of the base material, and the gel fraction of the pressure-sensitive adhesive layer is set within the above range. As a result, the initial adhesive strength to the adherend shows a good adhesive strength of 2 N / 20 mm or more, and the foaming agent expands and expands by heating, so that the adhesive strength to the adherend is greatly reduced. The adhesive strength at 160 ° C. for 1 minute is reduced to 0.3 N / 20 mm or less, and can be easily peeled and removed from the adherend.

In addition, the pressure-sensitive adhesive sheet thus peeled and removed has a pressure-sensitive adhesive layer made of a plant-derived material, so that when it is disposed of, carbon neutral can be achieved even if carbon dioxide is discharged, which may adversely affect the global environment. There are few things.

Next, examples of the present invention will be described in more detail. In the following, “parts” means parts by weight.

Further, the weight average molecular weight of the polyester polymer, the gel fraction of the adhesive layer, and the adhesive strength of the heat-peelable adhesive sheet are evaluated by the following methods.

<Weight average molecular weight>
After 0.01 g of a polyester polymer was weighed and added to 10 g of tetrahydrofuran (THF), it was left to dissolve for 24 hours. This solution was measured by gel permeation chromatography (GPC) (HLC-8220GPC manufactured by Tosoh Corporation) to determine the weight average molecular weight (Mw). The measurement conditions are as follows.

Column: G6000H6
Column size: 7.5mm 7ID x 30.0cmL
Eluent: THF
Flow rate: 0.300 ml / min Detector: RI
Column temperature: 40 ° C
Injection volume: 20 μl

<Gel fraction>
A sheet having a thickness of 50 μm in which a sample similar to the examples and the comparative examples was prepared without blending the foaming agent as a measurement piece was cut into a 5 cm × 5 cm square.

The cut sample was wrapped with a polytetrafluoroethylene (PTFE) sheet of known weight and weighed, and left in toluene at 23 ° C. for 7 days to extract the sol content in the sample. Then, it dried at 130 degreeC for 2 hours, and measured the weight after drying. The gel fraction was calculated by the following formula.

Gel fraction (%) = [(weight after drying−PTFE sheet weight) / (weight before drying−PTFE sheet weight)] × 100

<Adhesive strength>
A 25-μm thick polyester film (trade name “Lumirror S-10” manufactured by Toray Industries, Inc.) is attached to the adhesive surface of a heat-peelable pressure-sensitive adhesive sheet (cut to 20 mm in width) by one reciprocation of a 2 kg roller, and a tensile compression tester. (“TG-1kN” manufactured by Minebea Co., Ltd.), 180 ° peel adhesive strength (adhesive strength) before foaming and after foaming (N / 20 mm) (peeling speed: 300 mm / min, temperature: 23 ± 2 ° C., humidity: 65 ± 5% RH, which peels the polyester film). The heat treatment at the time of foaming was performed for 1 minute on a 160 ° C. hot plate.

Example 1
A three-necked separable flask is equipped with a stirrer, a thermometer, and a vacuum pump. To this, 108 g of dimer acid (trade name “Pripol 1009”, manufactured by Unikema), dimer diol (trade name “Plipol 2033”, manufactured by Mw537, Unikema) ) 105.6 g and 0.46 g of di-n-butyltin oxide (manufactured by Kishida Chemical Co., Ltd.) as a catalyst were charged, and the temperature was raised to 180 ° C. while stirring in a reduced pressure atmosphere, and this temperature was maintained. The reaction was continued for about 12 hours to obtain a polyester polymer. The weight average molecular weight Mw was 36,000.

To 100 parts of this polyester polymer, 2.5 parts of hexamethylene diisocyanate (trade name “TPA-100”, manufactured by Asahi Kasei Chemicals) as a crosslinking agent, foaming agent (trade name “Matsumoto Microsphere F-80SD”, Matsumoto Yushi 10 parts) were mixed to prepare an adhesive. This was applied to a polyethylene terephthalate (PET) sheet substrate and dried at 100 ° C. for 3 minutes. After drying, the release-treated surfaces of the PET sheet subjected to the release treatment were bonded together, and aging was carried out at 50 ° C. for 5 days to produce a heat-release-type pressure-sensitive adhesive sheet.

With respect to this pressure-sensitive adhesive sheet, when the gel fraction of the pressure-sensitive adhesive layer was measured after aging was completed, the gel fraction was 40%. The initial 180 ° peel adhesive strength in an unheated and unfoamed state was 5.7 N / 20 mm. The 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.05 N / 20 mm.

Example 2
A pressure-sensitive adhesive was prepared in the same manner as in Example 1 except that the amount of the crosslinking agent was 4 parts with respect to 100 parts of the polyester polymer, and a heat-peelable pressure-sensitive adhesive sheet was produced.

With respect to this heat-peelable pressure-sensitive adhesive sheet, when the gel fraction of the pressure-sensitive adhesive layer was measured after aging was completed, the gel fraction was 75%. The initial 180 ° peel adhesive strength in an unheated and unfoamed state was 3.9 N / 20 mm. The 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.02 N / 20 mm.

Example 3
A pressure-sensitive adhesive was prepared in the same manner as in Example 1 except that the amount of the crosslinking agent was 6 parts with respect to 100 parts of the polyester polymer, and a heat-peelable pressure-sensitive adhesive sheet was produced.

With respect to this heat-peelable pressure-sensitive adhesive sheet, when the gel fraction of the pressure-sensitive adhesive layer was measured after aging was completed, the gel fraction was 85%. The initial 180 ° peel adhesive strength in an unheated and unfoamed state was 2.2 N / 20 mm. The 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.05 N / 20 mm.

Example 4
A pressure-sensitive adhesive was prepared in the same manner as in Example 2 except that the blending amount of the foaming agent was changed to 5 parts with respect to 100 parts of the polyester polymer, and a heat-peelable pressure-sensitive adhesive sheet was produced.

The initial 180 ° peel adhesive strength of the heat-peelable pressure-sensitive adhesive sheet in an unheated and unfoamed state was 3.8 N / 20 mm. The 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.02 N / 20 mm.

Example 5
A pressure-sensitive adhesive was prepared in the same manner as in Example 2 except that the blending amount of the foaming agent was 30 parts with respect to 100 parts of the polyester polymer, and a heat-peelable pressure-sensitive adhesive sheet was produced.

The initial 180 ° peel adhesive strength of the heat-peelable pressure-sensitive adhesive sheet in an unheated and unfoamed state was 3.0 N / 20 mm. The 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.02 N / 20 mm.

Example 6
A pressure-sensitive adhesive was prepared in the same manner as in Example 2 except that the blending amount of the foaming agent was 50 parts with respect to 100 parts of the polyester polymer, and a heat-peelable pressure-sensitive adhesive sheet was produced.

The initial 180 ° peel adhesive strength of the heat-peelable pressure-sensitive adhesive sheet in an unheated and unfoamed state was 2.25 N / 20 mm. The 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.02 N / 20 mm.

Comparative Example 1
A pressure-sensitive adhesive was prepared in the same manner as in Example 1 except that the amount of the crosslinking agent was 2 parts with respect to 100 parts of the polyester polymer, and a heat-peelable pressure-sensitive adhesive sheet was produced.

With respect to this heat-peelable pressure-sensitive adhesive sheet, the gel fraction of the pressure-sensitive adhesive layer was measured after the aging was completed, and the gel fraction was 35%. The initial 180 ° peel adhesive strength in an unheated and unfoamed state was 7.5 N / 20 mm. Further, the 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.6 N / 20 mm. The adhesive strength after heat foaming was high, and peeling was difficult.

Comparative Example 2
A pressure-sensitive adhesive was prepared in the same manner as in Example 1 except that the amount of the crosslinking agent was 8 parts with respect to 100 parts of the polyester polymer, and a heat-peelable pressure-sensitive adhesive sheet was produced.

With respect to this heat-peelable pressure-sensitive adhesive sheet, the gel fraction of the pressure-sensitive adhesive layer was measured after completion of aging, and the gel fraction was 90%. The initial 180 ° peel adhesive strength in an unheated and unfoamed state was 0.7 N / 20 mm. The initial adhesive strength was too low, and it was difficult to hold the adherend. The 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.02 N / 20 mm.

Comparative Example 3
A pressure-sensitive adhesive was prepared in the same manner as in Example 2 except that the blending amount of the foaming agent was changed to 3 parts with respect to 100 parts of the polyester polymer to prepare a heat-peelable pressure-sensitive adhesive sheet.

The initial 180 ° peel adhesive strength of the heat-peelable pressure-sensitive adhesive sheet in an unheated and unfoamed state was 3.8 N / 20 mm. Further, the 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.6 N / 20 mm. The adhesive strength after heat foaming was high, and peeling was difficult.

Comparative Example 4
A pressure-sensitive adhesive was prepared in the same manner as in Example 2 except that the blending amount of the foaming agent was 70 parts with respect to 100 parts of the polyester polymer, and a heat-peelable pressure-sensitive adhesive sheet was produced.

The initial 180 ° peel adhesive strength of the heat-peelable pressure-sensitive adhesive sheet in an unheated and unfoamed state was 1.8 N / 20 mm. The initial adhesive strength was too low, and it was difficult to hold the adherend. The 180 ° peel adhesive strength in a foamed state after heating for 1 minute on a 160 ° C. hot plate was 0.02 N / 20 mm.

For each of the heat-peelable adhesive sheets of Examples 1 to 6 and Comparative Examples 1 to 4 above, together with the gel fraction of the adhesive layer and the amount of foaming agent (parts per 100 parts of the polyester polymer), the adhesive strength before heating (initial The adhesive strength after heating and the adhesive strength after heating (adhesive strength after heating and foaming) are shown in Table 1 below.

As is clear from the above results, each of the heat-peelable pressure-sensitive adhesive sheets of Examples 1 to 6 has high initial adhesive strength and can be easily peeled off with low adhesive strength after heating and foaming. On the other hand, each heat-peelable pressure-sensitive adhesive sheet of Comparative Examples 1 to 4 has an initial adhesive strength that is too low or an adhesive strength after heat foaming that is too high to satisfy both properties.

In addition to the above-described excellent characteristics, each heat-peelable pressure-sensitive adhesive sheet of Examples 1 to 6 can be expected to suppress an increase in CO2 even if incinerated, since the adhesive layer is derived from a plant.

Claims (1)

The gel fraction is 40 to 85% using a polyester polymer obtained by condensation polymerization of dimer acid , which is a plant-derived dicarboxylic acid , and dimer diol, which is a plant-derived diol , on at least one surface of the substrate. It has an adhesive layer is, in the adhesive layer, a polyester polymer per 100 parts by weight, the foaming agent of a thermally expandable microspheres are included 5 to 60 parts by weight, the initial adhesive strength is 2N / 20 mm or more A heat-peelable pressure-sensitive adhesive sheet having an adhesive strength after heating and foaming (160 ° C., 1 minute) of 0.3 N / 20 mm or less.