JP5622242B2 - Foam adhesive sheet - Google Patents

Description

  The present invention relates to a foamed pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one side of a foam, and is required to be easily peeled off during separation collection, recycling, etc., and further requires sealing properties, for example, electronic The present invention relates to a foamed pressure-sensitive adhesive sheet that can be suitably used in applications such as equipment, home appliances, houses, and automobile fields.

  In the fields of electronic devices, home appliances, houses, automobiles, and the like, adhesive tape has been frequently used for joining members because of excellent workability. And since it is excellent in the sealing performance and buffering property of a junction part, what used the foam as a base material is used suitably (patent document 1).

  When assembling precision parts such as mobile phones and personal computers, the requirements for sealing performance (sealing performance) and dimensional accuracy of joints are becoming stricter.

On the other hand, in recent years, attention has been paid to resource saving and recyclability in products due to increasing environmental awareness, and it is desirable that separation and collection be easy from the viewpoint of waste reduction.
Although the sealing material of Patent Document 1 is excellent in sealing performance to some extent, it cannot be said that re-peeling is still sufficient in terms of separation, it is difficult to peel off at the time of separation, and the foam is torn at the time of peeling. There was a problem that the foam was likely to remain.

Japanese Patent No. 4125875

  The purpose of the present invention is more excellent in sealing performance and flexibility such as followability and airtightness, maintaining appropriate adhesive force, and easy to peel off the adhesive sheet with consideration for environmental impact such as recyclability. It is providing the foaming adhesive sheet which provided the thickness.

  The inventor has intensively studied to achieve the above-described problems. As a result, it has been found that according to the foamed pressure-sensitive adhesive sheet in which a layer made of a specific pressure-sensitive adhesive composition is provided on a specific polyolefin resin foam, the above-mentioned problems can be achieved.

The present invention provides the following foamed adhesive sheet.
1 Adhesive to at least one surface of a polyolefin resin foam having an average cell diameter of 0.02 to 0.2 mm, an apparent density of 30 to 100 kg / m ³ , and a compressive stress of 10 to 90 KPa at 50% compression. A foamed pressure-sensitive adhesive sheet provided with a layer comprising an agent composition and having an adhesive strength of less than 5.0 N / 20 mm width in a 90-degree peel test.
2. A foamed pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive composition has a storage elastic modulus (G ′) at room temperature of less than 20 N / cm ² .
3. A foamed adhesive sheet, wherein the polyolefin resin foam has a tear strength in the range of 5 to 70 N / cm.
4. The foamed adhesive sheet, wherein the polyolefin resin foam is a polypropylene resin foam.
5 A foamed pressure-sensitive adhesive sheet, wherein the layer made of the pressure-sensitive adhesive composition has a thickness of 5 to 100 μm.

According to the present invention, the following remarkable effects can be obtained.
(1) The foamed pressure-sensitive adhesive sheet of the present invention has an average cell diameter of 0.02 to 0.2 mm, an apparent density of 30 to 100 kg / m ³ , and a compressive stress at 50% compression of 10 to 90 KPa. Because the foamed adhesive sheet is characterized in that a layer made of an adhesive composition is provided on at least one surface of the polyolefin resin foam, and the adhesive strength is less than 5.0 N / 20 mm width in a 90-degree peel test, Excellent flexibility and cushioning, excellent followability to adherend surface, excellent sealing performance, and can be easily and cleanly peeled, and excellent removability and recyclability. .
(2) When the pressure-sensitive adhesive composition is made of a pressure-sensitive adhesive composition having a storage elastic modulus (G ′) at room temperature of less than 20 N / cm ² , it further has appropriate initial adhesiveness and removability. Are better.
(3) When the tear strength of the polyolefin-based resin foam is in the range of 5 to 70 N / cm, the pressure-sensitive adhesive sheet is difficult to tear at the time of re-peeling and can be peeled off more neatly.
(4) When the polyolefin-based resin foam is a polypropylene-based resin foam, the pressure-sensitive adhesive sheet is excellent in strength of the foam and hardly peeled during re-peeling, and can be peeled off more neatly.
(5) When the thickness of the layer made of the pressure-sensitive adhesive composition is 5 to 100 μm, it has an appropriate adhesive force and is excellent in removability.
Therefore, the foamed pressure-sensitive adhesive sheet obtained by the present invention can be suitably used for applications such as sealing materials, packing materials, dustproof materials, and cushioning materials used in the fields of electronic equipment, home appliances, houses, automobiles, and the like.

  The foam used for the foamed pressure-sensitive adhesive sheet of the present invention contains a thermoplastic elastomer at a predetermined ratio in a polyolefin resin having a predetermined melt flow rate. The temperature dependence of the melt viscosity is relaxed, the foaming temperature is expanded and the foaming property is improved, carbon dioxide is used as the foaming agent, and an annular die having a bubble generation part and a foam molding part is used. In addition, by using a foam having good surface smoothness, which is made by foaming by extrusion and foaming at a predetermined discharge speed and pressure, the foam film strength is improved and the foaming ratio is improved, and at least the foam is used. By applying the pressure-sensitive adhesive layer on one side, it is possible to obtain a foamed pressure-sensitive adhesive sheet having excellent flexibility and cushioning properties.

It is a schematic sectional drawing of the annular die which shows one Embodiment of this invention.

(Polyolefin resin foam)
For the foamed adhesive sheet of the present invention, a polyolefin resin foam having excellent chemical resistance and flexibility is used. More specifically, the average cell diameter is 0.02 to 0.3 mm, and the apparent density is 30 to 100 kg / A polyolefin resin foam having a compression stress of 10 to 90 KPa at m ³ and 50% compression is used.
The foam structure of polyolefin resin foam can be any of closed cell structure, semi-closed semi-open cell structure, or open cell structure, but it has excellent followability to the adherend surface. To semi-independent semi-open cell structure and open-cell structure are preferable, and open-cell structure is more preferable.
If the average cell diameter of the polyolefin resin foam is small, the strength is insufficient, and if it is large, the flexibility, workability, and followability deteriorate, so it is limited to 0.02 to 0.3 mm. 0.03-0.2 mm is preferable and 0.03-0.18 mm is more preferable.

When the apparent density of the polyolefin resin foam is small, the mechanical strength of the polyolefin resin foam may be reduced. On the other hand, when the apparent density is large, the cushioning property or flexibility of the polyolefin resin foam may be reduced. Therefore, it is limited to ³⁰ to 100 kg / m ³ . It is preferably 30~90kg / ^{m 3,} more preferably 35~70kg / ^{m 3.}
If the compression stress of 50% compression of polyolefin resin foam is small, the followability to the surface of the adherend is inferior, so that the dustproof property and packing property cannot be maintained. On the other hand, if the compressive stress is large, the flexibility is inferior. In addition to being unable to maintain the properties, the cushioning properties and the buffering properties are also inferior, and therefore, limited to 10 to 90 Kpa. 15-80 Kpa is preferable and 15-75 Kpa is more preferable.
If the tear strength of the polyolefin resin foam is weak, the required strength will not be maintained, and it will cause tearing during use, while if it is too strong, the flexibility and follow-up will be inferior to prevent the entry of dust and dirt. Since the dust resistance and packing properties may not be maintained, the tear strength of polyolefin resin foam is the minimum and maximum values of MD direction (extrusion direction) and TD direction (direction orthogonal to the extrusion direction). It is preferably 5 to 70 N / cm, more preferably 8 to 65 N / cm, and particularly preferably 10 to 60 N / cm.

(Manufacturing method of polyolefin resin foam)
FIG. 1 is a schematic cross-sectional view of an annular die of one embodiment used for producing a polyolefin resin foam of the present invention.
The manufacturing method of the polyolefin-type resin foam which is one Embodiment of this invention is as follows.
A thermoplastic resin composition containing a cell nucleating agent in a compounded resin composition comprising 100 parts by weight of a polyolefin resin having a melt flow rate of 0.2 to 6 g / 10 min and 10 to 300 parts by weight of a thermoplastic elastomer is supplied to an extruder. Then, carbon dioxide is injected into the extruder as a foaming agent and kneaded with the molten resin composition, and then extruded and foamed from the annular die D shown in FIG. 1 attached to the tip of the extruder.
Particularly in this embodiment, the annular die D is continuous with the bubble generation unit 2 formed in the resin flow path 3 and the bubble generation unit 2, and grows the generated bubbles and smoothes the foam surface. A foam molding part 1, the resin discharge speed V in the bubble generation part 2 of the annular die D is 50 to 300 kg / cm ² · hr, and the resin pressure before the annular die D is Extrusion foaming is preferably performed under conditions of 7 MPa or more. 4 is an annular die-in side mold, and 5 is an annular die-out side mold.

In this specification, the resin discharge speed V (kg / cm ² · hr) is defined by the following equation.
V = extruded resin weight / mould bubble generating section cross-sectional area / time Here, the extruded resin weight refers to the total weight extruded from the mold. Therefore, the weight of the extruded resin is the total amount of the polyolefin resin composition and the foaming agent. Further, the weight of the extruded resin can be expressed by the discharge amount per hour (kg / hr).

  The resin pressure in front of the annular die is a pressure measured by a strain gauge or the like in the flow path from the tip of the extruder to the annular die. This is the value measured with a strain gauge attached to a straight pipe mold with flanges and a straight pipe mold connected in order with an annular die.

(Polyolefin resin)
A polyolefin resin having a melt flow rate of about 0.2 to 6 g / 10 min is preferably used. Polypropylene resins are preferred because of their excellent heat resistance and mechanical strength. Specific examples include homopolypropylene and copolymers of propylene and other olefins.
The copolymer of propylene and another olefin may be either a random copolymer or a block copolymer, but a block copolymer is preferred because of excellent heat resistance.
Examples of other olefins copolymerized with propylene include, in addition to ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, etc. And α-olefins having 4 to 10 carbon atoms.
Of these, homopolypropylene having excellent foamability and heat resistance and block copolymer polypropylene are preferable, and homopolypropylene having excellent heat resistance is more preferable.

Moreover, as polyolefin resin used for this invention, since it is excellent in foamability, it is preferable to use a high melt tension polypropylene resin. High melt tension polypropylene resins include high melt tension polypropylene (HMS-PP) that has free-end long-chain branching in the molecular structure, such as electron beam crosslinking, and high molecular weight components to increase melt tension. There are things. Commercially available products can be used as the high melt tension polypropylene, and specific examples of commercially available products include “Newstrain SH9000” manufactured by Nippon Polypro Co., Ltd., and “DaployWB135HMS” manufactured by Borealis.
The polyolefin resin may be used alone or in a suitable combination of two or more.

If the melt flow rate (MFR) of the polyolefin resin is low, the load on the extruder increases and the productivity decreases, or the molten polyolefin resin composition containing the foaming agent flows smoothly in the mold. However, when the surface is high, the resin pressure in front of the die ring die is lowered, and the ring die bubble generation part Since the resin pressure also decreases, bubbles are generated in front of the bubble generation part, and foaming is abruptly generated in the foam molded part, resulting in a decrease in foaming property, and the appearance of the resulting foam is reduced or foamed. Is not obtained, about 0.2 to 6 g / 10 min is preferable, 0.2 to 5 g / 10 min is more preferable, and 0.3 to 4 g / 10 min is particularly preferable.
In the present specification, the melt flow rate of a polyolefin-based resin refers to that measured at a test temperature of 230 ° C. and a test load of 21.18 N in accordance with JIS K7210: 1999 Method B.
The melt flow rate of a polyolefin resin refers to a value obtained by measuring the melt flow rate of the resin by the above method when a single polyolefin resin is used.
In addition, when two or more polyolefin resins are mixed and used, the melt flow rate of each polyolefin resin is measured by the above measuring method, and the value of each melt flow rate is determined as follows. , Means calculated.
That is, when the polyolefin resin is a mixture of n types of polyolefin resins, the melt flow rate of the polyolefin resin ₁ is MFR ₁ , the melt flow rate of the polyolefin resin 2 is MFR ₂ ,. The melt flow rate of the resin n is MFR _n , the content of the polyolefin resin 1 is C1, the content of the polyolefin resin 2 is C2,... The content of the polyolefin resin n is Cn. In addition, content of polyolefin resin n shall remove | divide the weight of polyolefin resin n by the weight of the whole polyolefin resin. And the melt flow rate of polyolefin resin is computed by a following formula.
Melt flow rate (g / 10min) = (MFR ₁ ) ^C1 x (MFR ₂ ) ^C2 x ... x (MFR _n ) ^Cn

(Thermoplastic elastomer)
It is preferable to mix a thermoplastic elastomer with the polyolefin resin.
A thermoplastic elastomer has a structure in which a hard segment and a soft segment are combined, has rubber elasticity at room temperature, and has the property of being plasticized and molded at a high temperature in the same manner as a thermoplastic resin. Generally, the hard segment is a polyolefin resin such as polypropylene or polyethylene, and the soft segment is a rubber component such as an ethylene-propylene-diene copolymer or an ethylene-propylene copolymer or amorphous polyethylene.
Thermoplastic elastomers are polymerization-type elastomers that are produced directly in a polymerization reaction vessel by polymerizing hard segment monomers and soft segment monomers; kneading machines such as Banbury mixers and twin screw extruders A blend type elastomer manufactured by physically dispersing a polyolefin resin that becomes a hard segment using a rubber and a rubber component that becomes a soft segment; using a kneading machine such as a Banbury mixer or a twin screw extruder By adding a crosslinking agent when physically dispersing the polyolefin resin to be used and the rubber component to be a soft segment, the rubber component is completely or partially crosslinked and microdispersed in the polyolefin resin matrix. Dynamically cross-linked elastomer And the like.

In the present invention, both a non-crosslinked elastomer and a crosslinked elastomer can be used. When a non-crosslinked elastomer produced by physically dispersing a rubber component that becomes a soft segment is used, the produced product is recycled. In consideration of the properties, it is possible to easily manufacture with an extruder similar to the case of extrusion foam molding of a normal polyolefin resin, and further, the foam molded product is recycled and supplied to the extruder again to perform the same foam molding. Even in this case, poor foaming due to the crosslinked rubber can be suppressed. On the other hand, when a crosslinked elastomer obtained by physically dispersing the rubber component serving as the soft segment and simultaneously partially or dynamically crosslinking the rubber component is used, it has excellent compatibility with the polyolefin-based resin, and can be obtained. It is preferable because the heat resistance of the foam is increased.
Examples of the diene component constituting the ethylene-propylene-diene copolymer elastomer include ethylidene norbornene, 1,4-hexadiene, dicyclopentadiene, and the like.
Here, the ethylene-propylene-diene copolymer elastomer may be used singly or in combination of two or more, and by using such an ethylene-propylene-diene copolymer elastomer, a normal polyolefin-based elastomer is used. Manufacture with an extruder similar to that in the case of extrusion foam molding of resin is facilitated.

The thermoplastic elastomer preferably has a durometer A hardness of 90 or less as defined in JIS K6253 from the viewpoint of obtaining a polyolefin resin foam having excellent flexibility. The duro A hardness is more preferably about 80 to 20.
If the amount of the thermoplastic elastomer contained in the polyolefin resin is small, the resulting polyolefin resin foam has poor buffering properties and flexibility, whereas if it is large, the rubber elasticity of the polyolefin resin composition becomes too strong. 10 to 300 parts by weight, preferably 20 to 150 parts by weight, more preferably 20 to 150 parts by weight, because foamability is reduced and shrinkage of the obtained polyolefin resin foam is increased. 30 to 100 parts by weight is particularly preferable.

(Bubble nucleating agent)
It is preferable to use a cell nucleating agent for the production of the polyolefin resin foam. The cell nucleating agent promotes the generation of cell nuclei when the polyolefin-based resin composition forms cells, and has an effect on the refinement and uniformity of the cells. Examples of the cell nucleating agent include talc, mica, silica, diatomaceous earth, alumina, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, Inorganic compounds such as barium sulfate, sodium hydrogen carbonate and glass beads; organic compounds such as polytetrafluoroethylene, azodicarbonamide, a mixture of sodium hydrogen carbonate and citric acid, and inert gases such as nitrogen. Among them, talc is preferable for inorganic compounds, and polytetrafluoroethylene is preferable for organic compounds because it has a high effect on bubble miniaturization. Further, it is particularly preferable that the polytetrafluoroethylene becomes a fibril when dispersed to increase the melt tension of the resin.

  When the amount of the cell nucleating agent is small, it is difficult to increase the number of cells of the obtained polyolefin resin foam, and the surface smoothness of the resulting polyolefin resin foam may be lowered. On the other hand, if the amount is too high, secondary aggregation tends to occur, and the surface smoothness of the foam due to poor extrusion foaming may decrease, so the amount may be 0.01 to 15 parts by weight with respect to 100 parts by weight of the compounded resin composition. Preferably, it is 0.1 to 12 parts by weight.

The cell nucleating agent used in the present invention may be mixed with the compounded resin composition in its own form as a polyolefin-based resin composition or separately supplied into the extruder, and further as a masterbatch with the compounded resin composition They may be mixed and supplied to the extruder as a polyolefin resin composition or individually.
The base resin of the masterbatch is not particularly limited as long as it has excellent compatibility with the compounded resin composition. For example, homopolypropylene, block polypropylene, random polypropylene, low density polyethylene, high density polyethylene and the like are preferable. Can be used.

(Additive)
In the polyolefin resin composition used in the present invention, various additives usually used for foam molding can be blended as optional components in addition to the polyolefin resin, the thermoplastic elastomer and the cell nucleating agent. Examples of the additive include a weather resistance stabilizer, a light stabilizer, a pigment, a dye, a flame retardant, a crystal nucleating agent, a plasticizer, a lubricant, a surfactant, a dispersant, an ultraviolet absorber, an antioxidant, and a filler. , Reinforcing agents, antistatic agents and the like. Of these, the surfactant imparts slipperiness and anti-blocking property. Moreover, a dispersing agent improves the dispersibility of an inorganic filler, for example, higher fatty acid, higher fatty acid ester, higher fatty acid amide etc. are mentioned.
The addition amount of the additive can be appropriately selected within a range not impairing the formation of bubbles and the physical properties of the resulting foam, and the addition amount used for molding a normal thermoplastic resin can be adopted.
The cell nucleating agent and the additive can be used as a master batch for ease of handling and prevention of contamination of the production environment due to powder scattering, and for improving dispersibility in a thermoplastic resin. .
The masterbatch can be usually performed by kneading an additive or the like in a thermoplastic base resin at a high concentration to form a pellet. The base resin is not particularly limited as long as it has excellent compatibility with the compounded resin composition. For example, homopolypropylene, block polypropylene, random polypropylene, low density polyethylene, high density polyethylene, and the like are preferably used. Can do.

(Foaming agent)
The foaming agent is supplied by being press-fitted into an extruder in order to foam the polyolefin-based resin composition. In the present invention, it is preferable to use carbon dioxide. Carbon dioxide can form finer bubbles than conventional foams by using supercritical, subcritical, or liquefied carbon dioxide, and the surface smoothness and flexibility of the resulting foams Can be improved.
The amount of the foaming agent that is press-fitted into the extruder may be adjusted as appropriate according to the expansion ratio of the polyolefin resin foam. However, if the amount is small, the expansion ratio of the polyolefin resin foam is reduced, and the weight and On the other hand, the heat insulation property may be lowered. On the other hand, if the amount is large, foaming may occur in the mold, resulting in bubble breakage, or large voids may be formed in the polyolefin resin foam. The amount is preferably about 1 to 10 parts by weight with respect to 100 parts by weight, more preferably about 2 to 8 parts by weight, and particularly preferably about 3 to 6 parts by weight.

(Extruder, mold and resin discharge speed)
In the method for producing a polyolefin resin foam of the present invention, any of a single screw extruder, a twin screw extruder, and a tandem type extruder can be used as the extruder. In the present invention, among these, a tandem type extruder is preferable because it is easy to adjust the extrusion conditions.

  An example of a mold used in the method for producing a polyolefin resin foam according to the present invention includes, as shown in FIG. 1 and the foregoing description, the bubble generation part 2 formed by the restriction 31 of the resin flow path 3 and the growth of the generated bubbles. And an annular die D having a foam molding part 1 for smoothing the foam surface. Since the polyolefin-based resin foam according to the present invention has finer bubbles than before, when foamed using a conventional annular die, a large number of corrugates are generated on the surface of the foam and obtained. The surface smoothness of the foam deteriorates. However, the annular die of the foam forming part can suppress the generation of corrugation in the bubble generating part and obtain a foam with a smooth surface by an appropriate slip resistance in the foam molded part. The corrugated herein refers to a number of ridges and valleys formed by undulation of the foam from the annular die to absorb the linear expansion in the circumferential direction due to volume expansion.

In the production method of the present invention, it is preferable that the resin discharge speed V at the bubble generation unit is 50 to 300 kg / cm ² · hr and the resin pressure before the annular die is 7 MPa or more.
The discharge speed V is more preferably about 70 to 250 kg / cm ² · hr, and particularly preferably about 100 to ²⁰⁰ cm ² · hr. In addition, the resin pressure before the annular die is preferably 7 MPa or more, and more preferably 8 MPa or more and 20 MPa or less. In addition to improving the foamability of the polyolefin-based resin by extrusion foaming under the above conditions, the bubbles can be refined and the strength of the cell membrane can be further increased. Under these conditions, the obtained foam is improved in workability in the case of secondary processing, and a sheet-like foam obtained by slicing is excellent in surface smoothness. When the discharge speed V is smaller than about 50 kg / cm ² · hr, it becomes difficult to obtain finer bubbles and a foam with a high expansion ratio. On the other hand, when it is larger than about 300 kg / cm ² · hr, the resin generates heat at the mold bubble generation part, causing bubble breakage, and the foaming ratio is likely to be lowered, and a corrugated corrugate is likely to be generated. This is not preferable because the diameter becomes uneven and the surface smoothness of the foam decreases. The discharge speed V is appropriately adjusted according to the cross-sectional area of the annular die bubble generating unit and the extrusion discharge amount.

  The method of adjusting the cross-sectional area of the bubble generating part includes changing the length of the bubble generating part of the mold (in the case of a flat mold) and the diameter (in the case of an annular die) and the interval between the bubble generating parts of the mold. There are two methods including a method of changing (in the case of a flat die or an annular die).

If the resin pressure in front of the annular die is lower than 7 MPa, bubble generation starts before the annular die bubble generation part and a good foam cannot be obtained, which is not preferable. On the other hand, if the pressure is higher than 20 MPa, the load on the extruder becomes too high, or the injection pressure of the foaming agent becomes too high, so that it is not possible to press-fit.
The resin pressure in front of the annular die is appropriately adjusted by the molten resin viscosity, the extrusion discharge amount, and the sectional area of the annular die bubble generating part. Furthermore, the molten resin viscosity is appropriately adjusted depending on the viscosity of the blended resin composition, the amount of foaming agent added, and the molten resin temperature. In this specification, the molten resin temperature refers to the temperature measured by a thermocouple attached in a direct contact with the molten resin in a straight pipe mold for measuring the resin pressure before the annular die. say.

  The resin temperature in the present invention is preferably in the range of 10 ° C. to 20 ° C. from the melting point of the polyolefin resin in order to improve foamability. When the resin temperature approaches the melting point, crystallization of the polyolefin-based resin starts, the viscosity rapidly increases, the extrusion conditions become unstable, and the load on the extruder increases, which is not preferable. On the other hand, if it is too high, the solidification of the resin after foaming does not catch up with the foaming speed, which causes problems such as foam breakage and foaming ratio not increasing.

(Foamed adhesive sheet)
The foamed pressure-sensitive adhesive sheet of the present invention is provided with a layer made of a pressure-sensitive adhesive composition on at least one surface of such a polyolefin resin foam, and the adhesive strength is less than 5.0 N / 20 mm width in a 90-degree peel test. is there.
If the adhesive strength of the foamed adhesive sheet is too strong, it will require complicated work at the time of peeling or recycling, and if it is too weak, the adhesive strength with the member cannot be maintained. It is limited to less than 1.0N / 20mm width and less than 5.0N / 20mm width in the 90 degree peel test.
Moreover, it is preferable that the adhesive force in a 180 degree | times peeling test is also less than 5.0 N / 20mm width. Since the adhesive strength in the 180 degree peel test is less than 5.0 N / 20 mm width, the foamed adhesive sheet can be peeled off more easily and more easily during recycling. The lower limit of the adhesive strength in the 180 degree peel test is preferably about 1 N / 20 mm width.
The pressure-sensitive adhesive composition preferably has a storage elastic modulus (G ′) at room temperature of less than 20 N / cm ² . This is because if the storage elastic modulus of the pressure-sensitive adhesive composition is too high, the adhesive residue may increase during reuse or recycling. More preferably less than 18N / cm ^2, more preferably less than 15N / cm ^2, particularly preferably less than 10 N / cm ^2.
On the other hand, if it is too low, adhesion to the material is weak and difficult to handle, so 0.5 N / cm ² or more is preferable.

(Adhesive composition)
The pressure-sensitive adhesive composition (also referred to as pressure-sensitive adhesive) used in the present invention is not particularly limited as long as it satisfies the above-mentioned pressure-sensitive adhesive force and storage elastic modulus. Such a pressure-sensitive adhesive can be selected from those generally used. For example, acrylic resin adhesives, rubber adhesives such as natural rubber and synthetic rubber, organic solvent adhesives mainly composed of silicone-based adhesive polymers, ethylene-vinyl acetate copolymer (EVA), etc. An emulsion-based pressure-sensitive adhesive having a main component can be mentioned. Among them, it is preferable to use an acrylic pressure-sensitive adhesive because it is excellent in durability and has little dirt during handling. These pressure-sensitive adhesives may be used alone or in combination of two or more. In addition, when the pressure-sensitive adhesive is applied to both surfaces of the foam, the pressure-sensitive adhesive applied to one surface and the pressure-sensitive adhesive applied to the other surface may be the same pressure-sensitive adhesive. Different pressure-sensitive adhesives may be used.

  These adhesives include isocyanate crosslinking agents, aziridine crosslinking agents, crosslinking agents such as metal complex compounds, tackifiers, coupling agents, fillers, softeners, plasticizers, surfactants, antioxidants. One or more of various additives such as a heat stabilizer, a light stabilizer, an ultraviolet absorber, a colorant, an antifoaming agent, a flame retardant, and an antistatic agent may be added.

When the thickness of the layer made of these pressure-sensitive adhesive compositions is too thick, it is difficult to adjust the adhesive residue and position. On the other hand, when the thickness is too thin, sufficient adhesive strength cannot be maintained. More preferably, it is 8-50 micrometers, and it is especially preferable that it is 10-40 micrometers.
[Physical property measuring method in the present invention]

(Average bubble diameter)
In the present specification, the average cell diameter of the polyolefin resin foam is measured as follows in accordance with the test method of ASTM D2842-69.
Specifically, the foamed sheet is cut along the MD direction (extrusion direction) and the TD direction (direction perpendicular to the extrusion direction), and the center of each cut surface is scanned by an electron microscope (manufactured by Hitachi, Ltd.). S-3000N) and enlarged.
Next, the photographed image is printed on A4 paper, and a straight line having a length of 60 mm is drawn on the image. The cut surface cut in the MD direction is parallel to the MD direction, the cut surface cut in the TD direction is parallel to the TD direction, and the VD direction (thickness direction) is perpendicular to the MD direction and the TD direction (sheet). Draw a straight line (perpendicular to). At this time, the magnification in the electron microscope was adjusted so that about 10 to 20 bubbles were formed on a straight line of 60 mm.
The average chord length (t) of the bubbles was calculated from the number of bubbles present on the straight line by the following formula, and the average chord length was defined as the average bubble diameter in each direction (MD direction, TD direction, and VD direction).
Average string length t = 60 / (number of bubbles × photo magnification)
When drawing a straight line, the straight line should be penetrated as much as possible without making point contact with the bubbles. Also, if some of the bubbles come into point contact with a straight line, this bubble is included in the number of bubbles, and if both ends of the straight line are located in the bubble without penetrating the bubbles Includes the bubbles in which both ends of the straight line are located in the number of bubbles.
Based on the average chord length t calculated by the above formula, the bubble diameter is calculated by the following formula.
Bubble diameter (mm) D = t / 0.616
The arithmetic average value of the obtained bubble diameter in the MD direction (D _MD ), the bubble diameter in the TD direction (D _TD ), and the bubble diameter in the VD direction (D _VD ) is defined as the average bubble diameter of the polyolefin resin foam. To do.
Average bubble diameter (mm) = (D _MD + D _TD + D _VD ) / 3

(Apparent density)
In this specification, the apparent density of the polyolefin-based resin foam is measured by a method based on the method described in JIS K 7222-1999. Specifically, a test piece of 10 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) is cut from the sample so as not to change the original cell structure of the sample, and its mass is measured. calculate.
Density (kg / m ³ ) = test piece mass (g) / test piece volume (cm ³ ) × 10 ³

(Peel test) (Adhesive strength)
In this specification, the peel test of the foamed adhesive sheet is performed by cutting the obtained foamed adhesive sheet into a width of 20 mm and a length of 150 mm, and reciprocating the acrylic sheet with a rubber roller weighing 2 kg. After standing at 23 ° C. and a humidity of 50% for 30 minutes, a 90-degree peel test and a 180-degree peel test were conducted at a test speed of 300 mm / min and a peel distance of 120 mm using a Tensilon universal testing machine UCT-10T manufactured by Orientec Corporation.

(Tear test)
In this specification, the tear test of a polyolefin resin foam is measured by a method based on the JIS K6767 1999 foam plastic-polyethylene test method. Specifically, the test piece described in JIS K6767 was allowed to stand for 24 hours under conditions of a temperature of 23 ° C. and a humidity of 50%, and then torn at a test speed of 500 mm / min. As a measuring apparatus, Tensilon universal testing machine UCT-10T marketed by Orientec can be used.
The strength in the MD direction (extrusion direction) and TD direction (direction perpendicular to the extrusion direction) was measured.

(Re-peeling test)
In this specification, the re-peeling test of the foamed adhesive sheet is performed by cutting the obtained foamed adhesive sheet into a width of 20 mm and a length of 100 mm, and reciprocating the acrylic sheet with a rubber roller weighing 2 kg. Allow to stand in a thermostatic bath at 60 ° C and 90% humidity for 48 hours, and leave it for 24 hours at 23 ° C and 50% humidity, then visually check the adhesive residue when the foamed adhesive sheet is peeled off It was evaluated on a five-point scale.
Evaluation criteria are as follows: ○: adhesive residue 0% to less than 5%, ○ △: adhesive residue 5% to less than 10%, Δ: adhesive residue 10% to less than 20%, Δ ×: adhesive residue 20% or more to Less than 40%, x: 40% or more of adhesive residue.
In consideration of reuse and recyclability, the adhesive residue at the time of re-peeling is preferably less than 20%, more preferably less than 10%, and particularly preferably less than 5%.

(Compression test)
In this specification, the compression test of the polyolefin resin foam is measured by a method based on the JIS K6767 foamed plastic-polyethylene test method. Specifically, the test piece cut into a 50 mm square was allowed to stand for 24 hours in an environment of a temperature of 23 ° C. and a humidity of 50%, and then compressed to 50% of the thickness at a test speed of 1 mm / min. As a measuring apparatus, Tensilon universal testing machine UCT-10T marketed by Orientec can be used.

(Storage modulus)
In this specification, the storage elastic modulus of the pressure-sensitive adhesive composition is TA
Measurement was performed using a viscoelasticity measuring apparatus AR2000ex manufactured by Instruments, and the test piece thickness was about 1 mm, the measurement temperature was room temperature (25 ° C.), the temperature increase rate was 3 ° C./min, and the frequency was 1 Hz.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited by these. In each example, parts and% are based on weight in principle.

Example 1
A tandem extruder was prepared by connecting a second extruder having a diameter of 75 mm to the tip of a first extruder having a diameter of 65 mm.
In the first extruder of this tandem type extruder, 100 parts by weight of polypropylene resin (MFR: 0.3 g / 10 min), EXLINK 3300B manufactured by JSR (MFR: non-crosslinked ethylene-propylene-diene copolymer elastomer) 10 parts by weight of a master batch (Talpet 70P manufactured by Nippon Talc Co., Ltd.) containing 70% by weight of talc having an average particle diameter of 12 μm as a cell nucleating agent in 100 parts by weight of a compounded resin composition obtained by adding 67 parts by weight of 0.9 g / 10 min) The thermoplastic resin composition mixed with was supplied to the first extruder and melt kneaded. In the middle of the first extruder, 4.2 parts by weight of carbon dioxide in a supercritical state is injected as a blowing agent, and the molten thermoplastic resin composition and carbon dioxide are mixed and kneaded uniformly. The molten resin composition contained was continuously supplied to the second extruder and cooled to a resin temperature suitable for foaming while being melt-kneaded. Thereafter, the diameter of the bubble generation part of the mold attached to the tip of the second extruder is 35 mm, the distance between the bubble generation parts of the mold is 0.25 mm (cross-sectional area of the bubble generation part: 0.275 cm ² ), and the distance between the foam molding parts Discharge rate of 30 mm / hr (discharge speed V = 109 kg / cm ² · hr) from an annular die having an outlet diameter φ70 of 3.4 mm and a foam molded part, a resin temperature of 175 ° C., and a resin pressure in front of the annular die Extruded and foamed under the condition of 8 MPa, and the cylindrical foam molded in the foam molding part of the annular die is attached onto the cooled mandrel, and the outer surface is cooled by blowing air from the air ring. The cylindrical foam was cut with a cutter at one point on the mandrel to obtain a sheet-like polypropylene resin foam. The foam had an average cell diameter of 170 μm and a density of 47.3 kg / m ³ . Both sides of the obtained polypropylene-based resin foam were sliced with a splitting machine (“AB-320D” manufactured by Fortuna) to remove the epidermis, and a sheet-like foam having a thickness of 1.0 mm on both sides as sliced surfaces. An acrylic pressure-sensitive adhesive 917 × 3A (Okabata Sangyo Co., Ltd., storage elastic modulus 1.2 N / cm ² ) was applied to a thickness of 16 μm on one side to obtain a foamed pressure-sensitive adhesive sheet.

(Example 2)
A tandem extruder was prepared by connecting a second extruder having a diameter of 75 mm to the tip of a first extruder having a diameter of 65 mm.
In the first extruder of this tandem type extruder, 100 parts by weight of polypropylene resin (MFR: 0.3 g / 10 min), a thermoplastic elastomer (non-crosslinked ethylene-propylene-diene copolymer elastomer) 10 parts by weight of a master batch (Talpet 70P manufactured by Nippon Talc Co., Ltd.) containing 70% by weight of talc having an average particle diameter of 12 μm as a cell nucleating agent in 100 parts by weight of a compounded resin composition obtained by adding 67 parts by weight of Z101N MFR: 14 g / 10 min) The thermoplastic resin composition in which the parts were mixed was supplied to the first extruder and melt-kneaded. In the middle of the first extruder, 4.8 parts by weight of supercritical carbon dioxide is injected as a foaming agent, and the molten thermoplastic resin composition and carbon dioxide are uniformly mixed and kneaded. The molten resin composition contained was continuously supplied to the second extruder and cooled to a resin temperature suitable for foaming while being melt-kneaded. Thereafter, the diameter of the bubble generation part of the mold attached to the tip of the second extruder is 35 mm, the distance between the bubble generation parts of the mold is 0.25 mm (cross-sectional area of the bubble generation part: 0.275 cm ² ), and the distance between the foam molding parts Discharge rate 30 kg / hr (discharge speed V = 109 kg / cm ² · hr), resin temperature 172 ° C., resin pressure in front of the annular die Extruded and foamed under the condition of 8 MPa, and the cylindrical foam molded in the foam molding part of the annular die is attached onto the cooled mandrel, and the outer surface is cooled by blowing air from the air ring. The cylindrical foam was cut with a cutter at one point on the mandrel to obtain a sheet-like polypropylene resin foam. The foam had an average cell diameter of 140 μm and a density of 45.7 kg / m ³ . Both sides of the obtained polypropylene-based resin foam were sliced with a splitting machine (“AB-320D” manufactured by Fortuna) to remove the epidermis, and a sheet-like foam having a thickness of 1.0 mm on both sides as sliced surfaces. On one side, an acrylic pressure-sensitive adhesive RA420 (manufactured by Kyowa Sangyo Co., Ltd., storage elastic modulus 5.8 N / cm ² ) was applied to a thickness of 30 μm to obtain a foamed pressure-sensitive adhesive sheet.

Example 3
The foam obtained in Example 2 was sliced with a splitting machine (“AB-320D” manufactured by Fortuna Co., Ltd.) to remove the epidermis, and a sheet-like foam having a thickness of 1.0 mm and a sliced surface on both sides. An acrylic pressure-sensitive adhesive RA460 (manufactured by Kyowa Sangyo Co., Ltd., storage elastic modulus 7.5 N / cm ² ) was applied to one side of the body to a thickness of 30 μm to obtain a foamed pressure-sensitive adhesive sheet.

Example 4
A tandem extruder was prepared by connecting a second extruder having a diameter of 75 mm to the tip of a first extruder having a diameter of 65 mm.
In the first extruder of this tandem type extruder, 100 parts by weight of a polypropylene resin (MFR: 0.5 g / 10 min), a thermoplastic elastomer (non-crosslinked ethylene-propylene-diene copolymer elastomer) 10 parts by weight of a master batch (Talpet 70P manufactured by Nippon Talc Co., Ltd.) containing 70% by weight of talc having an average particle diameter of 12 μm as a cell nucleating agent in 100 parts by weight of a compounded resin composition obtained by adding 67 parts by weight of Z101N MFR: 14 g / 10 min) The thermoplastic resin composition in which the parts were mixed was supplied to the first extruder and melt-kneaded. In the middle of the first extruder, 4.8 parts by weight of supercritical carbon dioxide is injected as a foaming agent, and the molten thermoplastic resin composition and carbon dioxide are uniformly mixed and kneaded. The molten resin composition contained was continuously supplied to the second extruder and cooled to a resin temperature suitable for foaming while being melt-kneaded. Thereafter, the diameter of the bubble generation part of the mold attached to the tip of the second extruder is 35 mm, the distance between the bubble generation parts of the mold is 0.25 mm (cross-sectional area of the bubble generation part: 0.275 cm ² ), and the distance between the foam molding parts Discharge rate 30kg / hr (discharge speed V = 109kg / cm ² · hr) from an annular die having an outlet diameter of 70 mm at a foam molded portion of 3.4 mm, a resin temperature of 174 ° C., a resin pressure before the annular die Extruded and foamed under the condition of 8 MPa, and the cylindrical foam molded in the foam molding part of the annular die is attached onto the cooled mandrel, and the outer surface is cooled by blowing air from the air ring. The cylindrical foam was cut with a cutter at one point on the mandrel to obtain a sheet-like polyolefin resin foam. The foam had an average cell diameter of 103 μm and a density of 42.5 kg / m ³ . An acrylic pressure-sensitive adhesive RA460 (manufactured by Kyowa Sangyo Co., Ltd., storage elastic modulus 7.5 N / cm ² ) was applied to one side of the obtained polypropylene resin foam to a thickness of 30 μm to obtain a foamed pressure-sensitive adhesive sheet.

(Example 5)
In the foam obtained in Example 4, both sides of the obtained polypropylene resin foam were sliced by a splitting machine (“AB-320D” manufactured by Fortuna) to remove the epidermis, and both sides having a thickness of 1.0 mm A foamed pressure-sensitive adhesive sheet was obtained by coating acrylic adhesive RA460 (manufactured by Kyowa Sangyo Co., Ltd., storage elastic modulus 7.5 N / cm ² ) to a thickness of 30 μm on one side of a sheet-like foam having a sliced surface.

(Comparative Example 1)
In the foam obtained in Example 2, both sides of the splitting machine (“A
B-320D ") to remove the epidermis and remove the epidermis. Acrylic adhesive 917x3B (Okabata Sangyo Co., Ltd., storage) A foamed pressure-sensitive adhesive sheet having an elastic modulus of 13.5 N / cm ² ) coated to a thickness of 27 μm was obtained.

(Comparative Example 2)
Both sides of the foam obtained in Example 1 are splitting machines (“A” manufactured by Fortuna)
B-320D ") to remove the epidermis and remove the epidermis. Acrylic adhesive 917 × 3C (Okabata Sangyo Co., Ltd., storage) A foamed pressure-sensitive adhesive sheet having an elastic modulus of 16.3 N / cm ² ) applied to a thickness of 32 μm was obtained.

(Comparative Example 3)
The foam obtained in Example 2 was sliced with a splitting machine (“AB-320D” manufactured by Fortuna Co., Ltd.) to remove the epidermis, and a sheet-like foam having a thickness of 1.0 mm and a sliced surface on both sides. A foamed pressure-sensitive adhesive sheet having a thickness of 30 μm applied to one side of the body with an acrylic pressure-sensitive adhesive G401 (manufactured by Kyowa Sangyo Co., Ltd., storage elastic modulus 11.0 N / cm ² ) was obtained.

(Physical property test)
About each Example and Comparative Example, 90 degree peeling test of foaming adhesive sheet, 180 degree peeling test of foaming adhesive sheet, tearing test of polyolefin resin foam, re-peeling test of foaming adhesive sheet, and 50 of polyolefin resin foam The% compressive stress was measured and compared. The comparison results are shown below.

  Table 1 shows the average cell diameter of the polyolefin resin foam, the density of the polyolefin resin foam, the thickness of the polyolefin resin foam, and the storage modulus of the layer made of the pressure-sensitive adhesive composition for each example and comparative example. The results are shown.

In this example, a polyolefin resin foam having fine bubbles, good foam density and sheet thickness and having a beautiful surface is obtained, and an adhesive layer is applied to at least one side of the obtained foam. Thereby, the foaming adhesive sheet which has the characteristics in adhesiveness, cushioning property, and buffering property is obtained. In this example, as shown in the table, it is shown that the 50% compressive stress is in the range of 10 to 90 KPa, and the peel test at 90 degrees is preferably less than 5.0 N / 20 mm.
In addition, the peel test at 90 degrees is less than 5.0 N / 20 mm and the storage elastic modulus is less than 20 N / cm ² , the adhesive residue at the time of re-peeling is less than 10%, and excellent re-peelability, It shows that the work at the time of recycling becomes easy. In Comparative Example 1, since the adhesive force was too strong, the adhesive residue at the time of re-peeling was as large as 40% or more. In Comparative Examples 2 and 3, since the adhesive force was strong, material destruction occurred, resulting in complicated operations during recycling.

  The present invention is characterized in that it has flexibility and followability to the adherend surface while maintaining excellent adhesiveness, and can be easily peeled off during fractional collection or recycling. These characteristics are required to be easily removed at the time of separation and collection, recycling, and the like, and can be suitably used in fields where adhesiveness is also required. Specifically, it can be suitably used as a cushioning material for houses, automobiles, etc., as a sealing material, a dustproof material or a buffer material for electronic devices and home appliances.

1: Foam molding part 2: Bubble generation part 3: Blowing agent-containing kneaded molten resin flow path part 4: Ring die-in side mold 5: Ring die-out side mold

Claims (4)

Average bubble diameter is 0.02-0.2 mm,
The apparent density is 30-100 kg / m ³ , and
A layer made of a pressure-sensitive adhesive composition is provided on at least one surface of a polyolefin-based resin foam having a compressive stress in the range of 10 to 90 KPa at 50% compression,
Its adhesive force is Ri der less than 5.0 N / 20 mm width at 90 ° peel test, was less than 5.0 N / 20 mm width at 180 degree peel test,
The storage elastic modulus (G ′) at room temperature of the pressure-sensitive adhesive composition is 7.5 N / cm ² or less.
Foamed pressure-sensitive adhesive sheet according to claim <br/> that is. The tear strength of the polyolefin resin foam is in the range of 5 to 70 N / cm.
The foamed pressure-sensitive adhesive sheet according to claim 1. The polyolefin resin foam is a polypropylene resin foam
The foamed pressure-sensitive adhesive sheet according to claim 1 or 2, wherein The foamed pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the layer made of the pressure-sensitive adhesive composition has a thickness of 5 to 100 µm.

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