JP2005139226A - Base sheet for adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a base sheet for adhesive sheet, having high air permeability, and letting no air bubbles left in between an adhesive and the mating adherend when an adhesive sheet is laminated on the adherend. <P>SOLUTION: The base sheet is obtained by the following process: a resin composition comprising a polyolefin resin (C) comprising 30-90 wt.% of a crystalline polypropylene (A) and 10-70 wt.% of a propylene-α-olefin copolymer (B) dispersed in the crystalline polypropylene (A) is melt-kneaded into a filmy melt, which is then formed into a filmy form, which is then at least unidirectionally oriented. The base sheet thus obtained has open pores communicating with the propylene-α-olefin copolymer (B) region. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a base sheet for pressure-sensitive adhesive sheets. More specifically, the present invention relates to a base sheet for pressure-sensitive adhesive sheets made of polyolefin resin which has high air permeability and hardly generates bubbles between the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet and the adherend when bonded to the adherend.

The pressure-sensitive adhesive sheet for labels, seals, etc. includes a surface sheet obtained by decorating a base sheet such as polyester resin, polyvinyl chloride resin, polyacrylic resin, polyolefin resin resin, etc., and a pressure-sensitive adhesive layer applied to the surface sheet. It consists of. Moreover, release paper is laminated as needed for the purpose of protecting the adhesive layer and supporting it during printing.
When these pressure-sensitive adhesive sheets are bonded to the adherend, air may be caught between the pressure-sensitive adhesive layer and the adherend, resulting in poor appearance on the construction surface. In addition, even after construction, gas and moisture contained in the adherend may be released and may accumulate between the pressure-sensitive adhesive layer and the adherend and cause swelling. In order to prevent these problems, skill is required for the laminating work, and much work is required for the work for repairing the swollen portion.

In order to discharge the gas remaining between the pressure-sensitive adhesive layer and the adherend, the following method is known.
(A) There is a method of providing air permeability by applying a perforating process with a pore diameter of about 200 μm after applying an adhesive layer to a top sheet and laminating release paper (see, for example, Patent Document 1). However, in this case, there is a problem that the surface appearance of the pressure-sensitive adhesive sheet is roughened by perforation, and the sheet breaking strength is lowered. Although there is a method of performing printing after punching for improving surface properties, there is a problem that the process becomes complicated.

(B) A glass bead or a granular material having a certain degree of hardness is added to the pressure-sensitive adhesive and then dispersed on the surface sheet. There is a method of adding a ventilation portion to the agent layer (see, for example, Patent Document 2). However, in this case, the pressure-sensitive adhesive sheet and the adherend are likely to be in point contact, and there is a problem that sufficient bonding strength cannot be obtained. Further, there is a problem that the additive sinks into the pressure-sensitive adhesive layer due to the bonding pressure, the convex portion disappears, the ventilation portion is blocked, and sufficient air permeability cannot be obtained at the central portion of the bonding.

(C) After applying the adhesive, there is a method of providing a ventilation portion to the adhesive layer by making a portion having a small thickness of the adhesive in a streaky or lattice shape by contacting a comb tooth plate or the like (for example, patent Reference 3). However, in this case, since the ventilation portion is unevenly distributed, it is necessary to make the ventilation portion relatively large. On the contrary, it causes air remaining, uneven strength of the bonded portion, and shape transfer to the top sheet is likely to occur. There is.

Japanese Utility Model Publication No. 07-18230 JP 08-113768 A JP 2002-221905 A

  An object of the present invention is to solve the above-mentioned problems, and has a high air permeability as compared with a conventional base sheet for pressure-sensitive adhesive sheets, and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet and the adherend when bonded to the adherend Another object of the present invention is to provide a base sheet for pressure-sensitive adhesive sheets in which air bubbles remain less likely to be generated.

  As a result of intensive studies, the inventors of the present invention contain a polyolefin resin (C) composed of crystalline polypropylene (A) and a propylene-α-olefin copolymer (B) dispersed in the crystalline polypropylene (A). For a pressure-sensitive adhesive sheet formed by melt-kneading a resin composition to form a film-shaped melt, forming the film-shaped melt into a film-shaped molding, and then stretching the film-shaped molding in at least one direction A base sheet, wherein the polyolefin resin (C) comprises 30 to 90% by weight of crystalline polypropylene (A) and 10 to 70% by weight of propylene-α-olefin copolymer (B), and propylene-α- The present invention was completed on the basis of the finding that this problem was solved by a base sheet for pressure-sensitive adhesive sheets having pores communicating with the olefin copolymer (B) region. In the present invention, the pores communicating with each other are pores that are continuously formed in the propylene-α-olefin copolymer (B) region, resulting in a path connecting both surfaces of the base sheet for the pressure-sensitive adhesive sheet. Say.

The present invention is constituted by the following.
1. A resin composition containing a polyolefin resin (C) composed of crystalline polypropylene (A) and a propylene-α-olefin copolymer (B) dispersed in the crystalline polypropylene (A) is melt-kneaded to form a film. A base sheet for pressure-sensitive adhesive sheets formed by forming a film-form melt into a film-form molding and then stretching the film-form molding in at least one direction, comprising a polyolefin resin (C ) Composed of 30 to 90% by weight of crystalline polypropylene (A) and 10 to 70% by weight of propylene-α-olefin copolymer (B) and communicated with the propylene-α-olefin copolymer (B) region. A substrate sheet for pressure-sensitive adhesive sheets having pores.

2. The melt flow rate ratio MFR _PP / MFR _RC of the melt flow rate MFR _PP of the crystalline polypropylene (A) and the melt flow rate MFR _RC of the propylene-α-olefin copolymer (B) is 0.1 to 10. 2. The substrate sheet for pressure-sensitive adhesive sheets according to item 1, characterized in that it is characterized in that

3. 3. The substrate sheet for pressure-sensitive adhesive sheets according to the item 2, wherein the melt flow rate ratio MFR _PP / MFR _RC is 0.2 to 5.

4). 4. The base sheet for pressure-sensitive adhesive sheets according to any one of 1 to 3 above, wherein a draft ratio when the film-shaped melt is formed into a film-shaped molded product is in the range of 1 to 10.

5). 4. The base sheet for pressure-sensitive adhesive sheets according to any one of 1 to 3, wherein a draft ratio when the film-shaped melt is formed into a film-shaped molded product is in the range of 1 to 3.

6). Any one of said 1-5 characterized by polyolefin resin (C) consisting of crystalline polypropylene (A) 40 to 70 weight% and polypropylene-alpha-olefin copolymer (B) 30 to 60 weight%. The base material sheet for adhesive sheets of 1 item | term.

7). The base material sheet for pressure-sensitive adhesive sheets according to any one of 1 to 6 above, wherein the propylene content of the propylene-α-olefin copolymer (B) is 30 to 80% by weight.

8). The base sheet for pressure-sensitive adhesive sheets according to any one of 1 to 6 above, wherein the propylene content of the propylene-α-olefin copolymer (B) is 40 to 70% by weight.

9. The polyolefin resin (C) is obtained by a multistage polymerization method including the steps of producing a crystalline polypropylene (A) in the first stage and continuously producing a propylene-α-olefin copolymer (B) in the second stage. 9. The substrate sheet for pressure-sensitive adhesive sheets according to any one of 1 to 8 above, which is characterized in that it is obtained.

10. 10. The substrate sheet for pressure-sensitive adhesive sheets according to any one of 1 to 9 above, wherein the air permeability resistance (Gurley) is 1 to 2,000 seconds / 100 ml.

11. The polyolefin resin (C) is composed of 30 to 70% by weight of the crystalline polypropylene (A) and 30 to 70% by weight of the propylene-α-olefin copolymer (B), and has a melt flow rate of the crystalline polypropylene (A). and MFR _PP, when propylene -α- olefin copolymer melt flow rate (B) was _{MFR RC,} wherein 1 wherein the ratio _MFR PP / _{MFR RC} melt flow rate is greater than 10 1,000 Base sheet for adhesive sheet.

12 12. The base sheet for an adhesive sheet according to the above item 11, wherein the draft ratio when the film-shaped melt is formed into a film-shaped molded product is in the range of 1 to 10.

13. 12. The substrate sheet for pressure-sensitive adhesive sheets according to 11 above, wherein the draft ratio when forming the film-shaped melt into a film-shaped molded product is in the range of 1 to 5.

14 14. The base sheet for pressure-sensitive adhesive sheets according to any one of 11 to 13, wherein the propylene content of the propylene-α-olefin copolymer (B) is 30 to 80% by weight.

15. 14. The base sheet for pressure-sensitive adhesive sheets according to any one of the above 11 to 13, wherein the propylene content of the propylene-α-olefin copolymer (B) is 40 to 70% by weight.

16. The polyolefin resin (C) is obtained by a multistage polymerization method including the steps of producing a crystalline polypropylene (A) in the first stage and continuously producing a propylene-α-olefin copolymer (B) in the second stage. 16. The base sheet for pressure-sensitive adhesive sheets according to any one of the above 11 to 15, wherein the base sheet is for pressure-sensitive adhesive sheets.

17. Air permeability resistance (Gurley) is 1-2000 second / 100ml, The base material sheet for adhesive sheets of any one of said 11-16 characterized by the above-mentioned.

18. 18. A pressure-sensitive adhesive sheet obtained by laminating a pressure-sensitive adhesive layer using the base sheet for pressure-sensitive adhesive sheets according to any one of 1 to 17 as a surface sheet.

  The substrate sheet for pressure-sensitive adhesive sheets of the present invention uses a specific polypropylene resin in which a propylene-α-olefin copolymer (B) is finely dispersed in crystalline polypropylene (A), and the polyolefin resin (C) is at a low temperature. It was obtained by improving the stretchability of the propylene-α-olefin copolymer (B) to form pores by cleavage of the propylene-α-olefin copolymer (B), and has excellent air permeability Have This base sheet is a base sheet for pressure-sensitive adhesive sheets in which bubbles are hardly generated between the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet and the adherend when the pressure-sensitive adhesive sheet using the base material is bonded to the adherend. In addition, the base sheet for pressure-sensitive adhesive sheets of the present invention has a simple resin composition and can be easily uniformly dispersed in the production process. It is a sheet.

Hereinafter, embodiments of the present invention will be described.
(1) Polyolefin resin The substrate sheet for pressure-sensitive adhesive sheets of the present invention includes crystalline polypropylene (A) and a propylene-α-olefin copolymer (B) (hereinafter referred to as “copolymer (B)”). And a polyolefin resin (C) in which a propylene-α-olefin copolymer (B) is finely dispersed as a region in a matrix of crystalline polypropylene (A).

(I) Crystalline polypropylene (A)
The crystalline polypropylene (A) is a crystalline polymer mainly composed of propylene polymerized units, preferably polypropylene having 90% by weight or more of propylene polymerized units. Specifically, it may be a propylene homopolymer, or may be a random or block copolymer of 90% by weight or more of propylene polymerized units and less than 10% by weight of an α-olefin. Examples of the α-olefin used when the crystalline polypropylene (A) is a copolymer include ethylene (included in the α-olefin in the present invention), 1-butene, 1-pentene, 1-hexene and 1-octene. 1-decene, 1-dodecene, 4-methyl-1-pentene, 3-methyl-1-pentene and the like. Among these, it is preferable from the viewpoint of production cost to use a propylene homopolymer or a propylene-ethylene copolymer having a propylene polymer unit content of 90% by weight or more.

The melt flow rate MFR _PP of crystalline polypropylene (A) is preferably in the range of 0.1 to 50 g / 10 min from the stability of film formation.

(ii) Propylene-α-olefin copolymer (B)
The copolymer (B) is a random copolymer of propylene and an α-olefin other than propylene. The content of propylene polymerized units is preferably in the range of 30 to 80% by weight, more preferably 35 to 75% by weight, still more preferably 40 to 70% by weight, based on the weight of the entire copolymer (B). is there. If the content of the propylene polymerized unit is within the above range, pores are easily formed in the region of the propylene-α-olefin copolymer (B) existing in the matrix of the crystalline polypropylene (A). It is easy to obtain characteristics as a base sheet for pressure-sensitive adhesive sheets.

  Examples of the α-olefin other than propylene used in the copolymer (B) include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 4-methyl-1. -Pentene, 3-methyl-1-pentene, etc. are mentioned. Among these, a propylene-ethylene copolymer using ethylene as an α-olefin is preferably used from the viewpoint of production cost.

The melt flow rate MFR _RC of the copolymer (B) is not particularly limited, but a range of 0.1 to 20 g / 10 minutes is preferable because it can be easily molded.

(iii) Polyolefin resin (C)
The polyolefin resin (C) is composed of crystalline polypropylene (A) and a copolymer (B). Melt flow rate ratio of melt flow rate MFR _PP of crystalline polypropylene (A) and melt flow rate MFR _{RC of} propylene-α-olefin copolymer (B) MFR _PP / MFR _RC (hereinafter referred to as “MFR ratio”) Is not particularly limited, but is preferably 0.1 to 1,000 from the viewpoint of moldability.

  In particular, when the MFR ratio is 0.1 to 10, particularly 0.2 to 5, the copolymer (B) is finely dispersed in the crystalline polypropylene (A), so fine and continuous pores are present. It is easy to obtain, the contact point between fine pores increases, and high air permeability resistance is easily obtained. Moreover, since it is excellent in stretchability, a base sheet for an adhesive sheet having a high porosity is obtained, and the air resistance is further increased.

  When the MFR ratio is larger than 10, the pore diameter of the pores formed by stretching is larger than that in the case where the MFR ratio is 0.1 to 10, and the proportion of the connected pores tends to decrease. Since the resin composition is not easily affected by fluctuations in film forming conditions and stretching conditions, it is easy to obtain a base sheet for an adhesive sheet having stable characteristics.

In the polyolefin resin (C), the content of the crystalline polypropylene (A) is 30 to 90% by weight, and the content of the copolymer (B) is 10 to 70% by weight. When the content of the copolymer (B) is less than 10% by weight, it is difficult to obtain the continuous pores of the present invention because the continuous pores formed in the copolymer (B) region is reduced. When it exceeds 70% by weight, it becomes difficult to obtain a finely dispersed structure of the copolymer (B) present in the crystalline polypropylene (A).
When the MFR ratio is 0.1 to 10, the content of the crystalline polypropylene (A) in the polyolefin resin (C) is preferably 40 to 70% by weight, and the content of the copolymer (B) is 30 to 30%. 60% by weight is preferred.
When the MFR ratio is greater than 10, the content of the crystalline polypropylene (A) in the polyolefin resin (C) is preferably 30 to 70% by weight, and the content of the copolymer (B) is 30 to 70% by weight. preferable. If the content of the crystalline polypropylene (A) and the copolymer (B) is in the above range, continuous pores are obtained and the dispersibility of the copolymer (B) is good.

  The production method of the polyolefin resin (C) is not particularly limited, and any production method may be used as long as the above conditions are satisfied. For example, the polyolefin resin (C) may be produced by mixing the crystalline polypropylene (A) and the copolymer (B) obtained by separately polymerizing by melt kneading or the like. Specifically, a copolymer (B) polymerized using a Ziegler-Natta catalyst such as a titanium-supported catalyst or a commercially available ethylene-propylene rubber corresponding to the copolymer (B) and crystalline polypropylene (A) are melted. The method of mixing can be illustrated.

  Alternatively, the polyolefin resin (C) may be produced by continuously polymerizing the crystalline polypropylene (A) and the copolymer (B) by multistage polymerization. For example, by using a plurality of polymerization vessels, a crystalline polypropylene (A) is produced in the first stage, and then a copolymer (B) is produced in the presence of the crystalline polypropylene (A) in the second stage. The method of manufacturing resin (C) continuously is mentioned. This continuous polymerization method is lower in production cost than the melt mixing method described above, and a polyolefin resin (C) in which the copolymer (B) is uniformly dispersed in the crystalline polypropylene (A) can be stably obtained. Therefore, it is preferable.

  In the present invention, a particularly preferred polyolefin resin (C) is produced by the above continuous polymerization method and adjusted so that the MFR ratio is 10 or less, more preferably in the range of 0.2 to 5. By setting the MFR ratio within this range, the copolymer (B) is uniformly and finely dispersed in the crystalline polypropylene (A). Therefore, when the polyolefin resin (C) is stretched, the crystalline polypropylene is used. Uniform and fine pores are generated in the copolymer (B) region dispersed in (A), and as a result, an excellent base sheet for pressure-sensitive adhesive sheets having a high air resistance is obtained.

  In the substrate sheet for pressure-sensitive adhesive sheets of the present invention, many fine cleavages are observed in the copolymer (B) region finely dispersed in the crystalline polypropylene (A). Since the copolymer (B) having compatibility with the crystalline polypropylene (A) has a lower strength than the crystalline polypropylene (A), it is assumed that cleavage occurred in the copolymer (B) region due to stretching stress. The This mechanism is achieved by stretching a film formed by mixing a conventional polyolefin resin with inorganic fillers such as silica and talc, and organic fillers such as polyolefin and incompatible nylon and polyethylene terephthalate, at least in one direction to form a matrix polymer. This is fundamentally different from the method of generating voids (pores) at the interface between the filler and the filler. As a result, the obtained base sheet for pressure-sensitive adhesive sheets has a small average pore diameter and a high air resistance. It has become.

  In the present invention, the copolymer (B) region means a region occupied by the copolymer (B) itself and a boundary region between the copolymer (B) and a substance adjacent thereto. Therefore, the pores generated in the copolymer (B) region include pores due to cleavage generated in the region occupied by the copolymer (B) itself, and the crystalline polypropylene (A) and the copolymer (B). And pores due to interfacial delamination that occur in the boundary region.

Specifically, the polyolefin resin (C) having the MFR ratio as described above can be produced by a method described in International Publication WO 97/19135, Japanese Patent Laid-Open No. 8-27238, or the like.
In addition, the polyolefin resin (C) can be produced by the above-described method, and one having a desired specification may be selected from commercially available products.

The MFR ratio is usually determined by measuring the MFR _PP of the crystalline polypropylene (A) and the MFR _RC of the copolymer (B), but when the polypropylene resin is continuously produced by multistage polymerization. In the case where the crystalline polypropylene (A) is first polymerized and then the copolymer (B) is polymerized, the MFR _RC of the copolymer (B) cannot be directly measured. From the MFR _{PP of} A), the melt flow rate MFR _{WHOLE of} the resulting polyolefin resin (C) and the content W _RC (% by weight) of the copolymer (B) in the polyolefin resin (C), the following formula can be used. it can.
log (MFR _RC ) = {log (MFR _WHOLE ) − (1−W _RC / 100) log (MFR _PP )} / (W _RC / 100)

(2) Resin composition for forming base material sheet for pressure-sensitive adhesive sheet The resin composition, which is a molding material for the film-shaped molded product for forming the base material sheet for pressure-sensitive adhesive sheet of the present invention, is mainly composed of polyolefin resin (C). In addition, surfactants such as antioxidants, neutralizers, α crystal nucleating agents, β crystal nucleating agents, hindered amine weathering agents, ultraviolet absorbers, antifogging agents and antistatic agents used in ordinary polyolefins. An agent, an inorganic filler, a lubricant, an antiblocking agent, an antibacterial agent, an antifungal agent, a fluorescent agent, a pigment, and the like can be blended as necessary. In the present invention, the main component means the most abundant component.

  Antioxidants include tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, 2,6-di-t-butyl-4-methylphenol, Phenolic compounds such as n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate and tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate Antioxidant, or tris (2,4-di-t-butylphenyl) phosphite, tris (nonylphenyl) phosphite, distearyl pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) Examples thereof include phosphorus-based antioxidants such as -4,4'-biphenylene-diphosphonite.

  Examples of neutralizing agents include higher fatty acid salts such as calcium stearate. Examples of inorganic fillers and anti-blocking agents include calcium carbonate, silica, hydrotalcite, zeolite, aluminum silicate, magnesium silicate, and the like. Can be exemplified by higher fatty acid amides such as stearic acid amide, and the antistatic agent can be exemplified by fatty acid esters such as glycerol monostearate.

  Alpha crystal nucleating agents include talc, aluminum hydroxy-bis (4-t-butylbenzoate), 1,3,2,4-dibenzylidene sorbitol, 1,3,2,4-bis (p-methylbenzylidene) Sorbitol, 1,3,2,4-bis (p-ethylbenzylidene) sorbitol, 1,3,2,4-bis (2 ′, 4′-dimethylbenzylidene) sorbitol, 1,3,2,4-bis ( 3 ', 4'-dimethylbenzylidene) sorbitol, 1,3-p-chlorobenzylidene-2,4-p-methylbenzylidenesorbitol, 1,3,2,4-bis (p-chlorobenzylidene) sorbitol, sodium-bis (4-t-Butylphenyl) phosphate, sodium-2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate Calcium-2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate, aluminum dihydroxy-2,2′-methylene-bis (4,6-di-t-butylphenyl) Known α-crystal nucleating agents such as phosphate can be used. These may be used alone or in combination of two or more.

  Although the compounding quantity of these additives can be suitably selected according to the purpose of use of the base sheet for the pressure sensitive adhesive sheet, it is usually preferably about 0.001 to 5% by weight with respect to the total amount of the resin composition.

  The resin composition for forming the base sheet for the pressure-sensitive adhesive sheet of the present invention has a propylene homopolymer and a single amount other than propylene containing propylene as a main component, as long as the effects of the present invention are not impaired. Two or more random polymers with the body and other olefin resins such as polyethylene resin, polybutene resin, and polymethylpentene resin may be used in combination.

  Further, an ethylene-diene elastic copolymer, ethylene-propylene elastic copolymer, styrene polymerized with a single site catalyst or a known multi-site catalyst in order to lower the softening temperature of the resin composition or improve flexibility. -An elastic copolymer such as a butadiene elastic copolymer may be added.

  The method for blending the polyolefin resin (C) and the above additives is not particularly limited, and is blended by a usual blending device such as a mixer with a high-speed stirrer such as a Henschel mixer (trade name), a ribbon blender, and a tumbler mixer. A method (dry blending) can be exemplified, and further a pelletizing method using a normal single screw extruder or twin screw extruder can be exemplified.

(3) Formation of base material sheet for pressure-sensitive adhesive sheet The base material sheet for pressure-sensitive adhesive sheet of the present invention is obtained by melt-extruding the resin composition mainly composed of polyolefin resin (C) to form a film-like molded product with a low draft ratio. After molding, the film-like molded product can be formed by stretching in at least one direction at a temperature of 100 ° C. or lower. The process consists of a film forming process and a stretching process. The main component is the most abundant component.

(i) Film-forming process In the film-forming process for obtaining a film-shaped molded product from the resin composition, methods such as a known inflation film molding method, T-die film molding method, and calendar molding method are used. A T-die film forming method with high thickness accuracy and easy multilayering is preferably used.

  The resin composition can be formed at an extrusion molding temperature of 180 ° C. or higher, but the purpose is to reduce the pressure inside the die and reduce the draft ratio described later, and the rigidity of the crystalline polypropylene (A) as a matrix. An extrusion temperature of 220 to 300 ° C. is preferably used in order to improve and facilitate formation of uniform and fine pores in the copolymer (B) region dispersed in the crystalline polypropylene (A).

The melt-kneaded resin composition is extruded from the die lip. At this time, the linear velocity V _{CL in} the flow direction (MD) of the resin composition passing through the die lip and the flow direction (MD) line of the film-shaped molded product The draft ratio (V _CL / V _f ) defined by the ratio of the speed V _f is an important factor for achieving the present invention. Generally, the draft ratio is about 10 to 50 when a thermoplastic resin film is formed. In the present invention, the draft ratio when forming the resin composition is 1 to 10, and the resulting film-like molded product is excellent in stretchability, and fine continuous pores are easily formed by stretching. Become.

  In order to improve the rigidity of the crystalline polypropylene (A) as a matrix and to make uniform and fine pores easily generated in the copolymer (B) region dispersed in the crystalline polypropylene (A), The cooling of the extruded film-shaped product is desirably slow cooling, and in the case of inflation molding, the air volume during cooling is reduced. In the T-die film molding method, the temperature of the cooling roll is 60 to 120 ° C., More preferably, it is desirable to cool in the range of 70 to 110 ° C. If the temperature of the cooling roll is within the above range, the desired porosity can be easily obtained, and the molten resin does not adhere to the roll and does not impair the productivity of the film.

  The thickness of the film-like molded product obtained in the film-forming process is not particularly limited, but is determined by the stretching and heat treatment conditions in the next stretching process and the required characteristics of the use of the porous film, and preferably 20 μm to 2 mm. 50 to 500 μm is more preferable, and the film forming speed is preferably in the range of 1 to 100 m / min. Film-shaped molded articles having these thicknesses are obtained by various film forming apparatuses composed of a combination of the cooling roll and an air knife having an air outlet, the cooling roll and a pair of metal rolls, the cooling roll and a stainless belt, and the like. .

  Furthermore, the base sheet for the pressure-sensitive adhesive sheet of the present invention is formed by coextruding a resin composition containing a known inorganic filler, organic filler, etc. with the resin composition for forming a base sheet for pressure-sensitive adhesive sheets of the present invention. It may be a molded product. In this case, the polymer constituting the resin composition containing a filler or the like is preferably a polyolefin resin such as a polypropylene resin or a polyethylene resin from the viewpoint of compatibility.

  In addition, you may heat-process in order to further improve a crystallinity degree before using for the obtained film-form molding to the next extending process. The heat treatment is performed, for example, by heating at a temperature of about 80 to 150 ° C. for about 1 to 30 minutes with a heated air circulation oven or a heating roll.

(ii) Stretching process The film-shaped molded product formed in the film-forming process is then stretched in at least one of the machine direction (MD) direction or the transverse (TD) direction, and into the crystalline polypropylene (A). Fine pores of about 0.01 to 10 μm communicating with the finely dispersed copolymer (B) region are formed. In this respect, the production method of the present invention is fundamentally different from the conventional single-component stretching method, multi-component stretching method, mixed extraction method and the like. As a result, the production method of the present invention can be found in complicated extraction and drying processes such as the mixed extraction method, and single component stretching methods in which pores are expressed by fibrillation between lamellar crystals of crystalline polyolefin. A crystallization step by heat treatment after film formation is not necessarily required, and in the case of the multi-component stretching method in which voids are generated at the interface between the crystalline polyolefin and the filler, the stretchability is poor and the average pore diameter tends to increase. Problems such as low are greatly improved, and it becomes possible to provide a base sheet for an adhesive sheet having an arbitrary average pore diameter, porosity, and air permeability resistance with excellent productivity.

  In addition to the uniaxial stretching method of stretching in one direction, the stretching method includes a sequential biaxial stretching method of stretching in the other direction after stretching in one direction, a simultaneous biaxial stretching method of stretching simultaneously in the longitudinal and transverse directions, and There are a method of performing multistage stretching in a uniaxial direction, a method of further stretching after sequential biaxial stretching and simultaneous biaxial stretching, and any method may be used. In addition, since the film-shaped molded product is drafted in the film-forming step, even if the film-shaped molded product is formed at a low draft ratio, a copolymer (which is finely dispersed in the crystalline polypropylene (A) ( B) is oriented along the flow direction, and the first-stage stretching is preferably performed by a uniaxial stretching method in the transverse direction or a simultaneous biaxial stretching method in the longitudinal and transverse directions.

The first stage stretching temperature is preferably lower than the melting point T _mα of the copolymer (B), and a temperature range of 10 to 100 ° C. is preferably used. In the present invention, the polyolefin resin (C) is specified. It was found that by using the composition, the stretchability in these low temperature regions was excellent. Further, the draw ratio is not particularly limited and is determined from the required properties of the application of the second-stage drawing conditions and the base sheet for the pressure-sensitive adhesive sheet, which is performed as necessary. 7 times. If the draw ratio is in this range, a base sheet for pressure-sensitive adhesive sheets having excellent characteristics can be obtained, and there is no risk of a decrease in productivity due to frequent stretching. In the case of simultaneous biaxial stretching, the area ratio (= longitudinal stretching ratio × lateral stretching ratio) is preferably 2 to 50 times, and more preferably 4 to 40 times. If the area magnification is in this range, a base sheet for pressure-sensitive adhesive sheets having excellent air permeability resistance can be obtained, and there is no fear of a decrease in productivity due to frequent stretching breaks.

The base sheet for pressure-sensitive adhesive sheets of the present invention performs second-stage stretching as necessary, and the second-stage stretching temperature is preferably 10 ° C. or more lower than the melting point T _{mc of} crystalline polypropylene (A). Moreover, when this _{extending | stretching} temperature is higher than melting _| fusing point Tm ( _alpha ) of a copolymer (B), there exists a tendency for the porosity not to increase so much and to reduce the thickness of the base material sheet for adhesive sheets obtained. Furthermore, when the _stretching temperature is lower than T _mα , the porosity increases, but the thickness tends not to decrease much.

  The stretching ratio in the second stage is determined by the air resistance of the base sheet for the pressure-sensitive adhesive sheet, but is generally 1.5 to 7 times. If the stretching ratio is within the above range, the stretching effect is sufficient. Thus, there is no reduction in productivity due to stretching.

  It is preferable that the membrane-shaped molded product that has been formed into pores by the above stretching step and then becomes porous is then heat-treated. This heat treatment is mainly intended for heat fixation for maintaining the formed pores, and is usually carried out on heating rolls, between heating rolls or through a hot air circulating furnace.

In this heat treatment (heat setting), the film-like molded product that has become porous while maintaining the stretched state is heated to a temperature 5 to 60 ° C. lower than the melting point T _mc of the crystalline polypropylene (A). It is carried out by setting it to 50%. If the heating temperature is within the above range, the formed pores will not be clogged, the heat setting is insufficient and the pores will be closed later, or the temperature changes when used as a base sheet for pressure-sensitive adhesive sheets There is no risk of heat shrinkage.

  Although the thickness of the base material sheet for adhesive sheets of this invention is not specifically limited, About 10-200 micrometers is preferable from a viewpoint of productivity. When the thickness is within the above range, the air resistance is good and the productivity is good.

  The base sheet for the pressure-sensitive adhesive sheet of the present invention can be subjected to a hydrophilic treatment such as a surfactant treatment, a corona discharge treatment, a low temperature plasma treatment, a sulfonation treatment, an ultraviolet treatment, a radiation graft treatment, if necessary. Various coating films can be formed.

  In order to produce a pressure-sensitive adhesive sheet using the substrate sheet for pressure-sensitive adhesive sheets of the present invention, a decorative treatment such as printing is applied to one side of the base material sheet as necessary, and a pressure-sensitive adhesive is applied to the surface not subjected to the decorative treatment. A method of applying a layer is used.

  The surface decoration treatment method can be appropriately selected from known methods depending on the purpose of use of the base sheet for the pressure-sensitive adhesive sheet. Although a part of the pores due to the coated material such as printing ink may be blocked, generally the printing area is a small range, and air permeability is not impaired. Moreover, in the case of whole surface application, there is also a method for restoring air permeability by air blowing from the base sheet side after application.

  As a method for applying the pressure-sensitive adhesive layer, in addition to a method of applying the pressure-sensitive adhesive in a pattern such as a dot for the purpose of maintaining air permeability, a surface obtained by adding water, air, or a foaming agent to the pressure-sensitive adhesive solution is used. A method of applying a vent to the pressure-sensitive adhesive layer by applying it to a sheet and forming the pressure-sensitive adhesive layer in a porous form by bubbles generated by gas expansion due to heat in the drying process or by forming the pressure-sensitive adhesive into a nonwoven fabric. is there. When laminating, the pressure-sensitive adhesive has fluidity, so the ventilation part may be partially blocked by the pressure of laminating, but by having air permeability over the entire pressure-sensitive adhesive sheet, bubbles may remain. Absent.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these.
The polyolefin resin (C) used in Examples and Comparative Examples polymerizes crystalline polypropylene (A) at the first stage by a continuous polymerization method, and copolymer (B) (propylene-ethylene copolymer at the second stage. Polymer) was obtained by polymerizing.
In addition, the measurement and evaluation in an Example and a comparative example were implemented with the following method.

(1) Porosity: A sample of 100 × 100 mm is cut out from the base sheet for pressure-sensitive adhesive sheets, the weight and thickness are measured to determine the bulk specific gravity, and the non-porous porous molded product 100 × 100 mm before stretching The true specific gravity was determined using an automatic specific gravity meter DENSIMETER DS (trade name) manufactured by Toyo Seiki Seisakusho, and the porosity was determined from the following formula.
Porosity (%) = (1-bulk specific gravity / true specific gravity) × 100

(2) Melt flow rate (MFR): Measured in accordance with JIS K 7210 under conditions of a temperature of 230 ° C. and a load of 21.18N.

(3) Air permeability resistance (Gurley): An index indicating air permeability, and the time required for 100 ml of air to pass through was measured with a B-type Gurley densometer (manufactured by Tester Sangyo Co., Ltd.) in accordance with JIS P 8117. .

(4) Stretchability: A test piece having a length of 40 mm and a length of 100 mm and having a length direction of the longitudinal direction (MD) or a transverse direction (TD) was prepared from a film-shaped molded article. The test piece was stretched uniaxially every 0.5 times in the length direction under the conditions of a stretching temperature of 23 ° C. and a deformation rate of 200% / second, and the stretch ratio not to stretch and break was defined as the stretchable ratio, and the stretchability was evaluated. . The higher the stretchable ratio, the better the stretchability, and the easier it is to form a film-like molded product, the higher the porosity is.

(5) Bubble remaining:
A pressure-sensitive adhesive sheet was prepared by applying an acrylic pressure-sensitive adhesive to the base sheet for the pressure-sensitive adhesive sheet in a dot pattern so as to have a coating thickness of 100 μm and drying at 110 ° C. for 2 minutes. This pressure-sensitive adhesive sheet was placed on a smooth acrylic plate and pasted from the end toward the center using a hand squeegee (resin spatula), and the air bubbles remaining between the pressure-sensitive adhesive and the adherend were visually observed at the center. .
◎: No air bubbles left ○: No air bubbles left (Bubbles are generated during work, but disappear when pressed from above)
×: Bubble remaining

1) Preparation of resin composition for forming base material sheet for pressure-sensitive adhesive sheet Using polyolefin resin (C) shown in Example 1 of Table 1, tetrakis [methylene-3- ( 3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] 0.1% by weight of methane, tris (2,4-di-t-butylphenyl) phosphite as a phosphorus antioxidant 0.1% by weight, 0.1% by weight of calcium stearate as a neutralizing agent, mixed with a Henschel mixer (trade name), melt-kneaded using a twin screw extruder (caliber 50 mm), pelletized, and adhered A resin composition for forming a base sheet for a sheet was obtained.

2) Preparation of substrate sheet for pressure-sensitive adhesive sheet [Film forming process / Creation of unstretched film-shaped molded product]
Using a 20 mm extruder equipped with a T die with a lip width of 120 mm, the above pellet-shaped resin composition was melted at an extrusion temperature of 280 ° C. and a discharge rate of 4 kg / h, and the lip clearance was adjusted to 0.40 mm. The film was further extruded into a film and cooled and solidified on a cooling roll at 80 ° C. to prepare a film-shaped molded product having a width of 100 mm and a thickness of 400 μm. When the film-like molded product in a molten state was cooled and solidified, the non-contact surface with the cooling roll was air-cooled with an air knife.
Table 1 shows the evaluation results of the stretchability of the obtained film-like molded product.

3) [Stretching process / Preparation of base sheet for pressure-sensitive adhesive sheet]
The film-shaped molded product is stretched in the transverse direction (TD direction) under the conditions of a stretching temperature of 23 ° C., a deformation rate of 200% / second, and a stretching ratio of 3 times while constraining the machine direction (MD direction). The base material sheet for pressure-sensitive adhesive sheets made of polyolefin resin was obtained by stretching in the machine direction (MD direction) under conditions of a stretching temperature of 100 ° C., a deformation rate of 1,000% / second, and a stretching ratio of 3 times. Table 1 shows the properties of the obtained base sheet for pressure-sensitive adhesive sheets.

  Except having used polyolefin resin (C) shown in Example 2 of Table 1, the base material sheet for adhesive sheets was obtained according to Example 1. FIG. Table 1 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  Except having used polyolefin resin (C) shown in Example 3 of Table 1, the base material sheet for adhesive sheets was obtained according to Example 1. FIG. Table 1 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  Except having used polyolefin resin (C) shown in Example 4 of Table 1, the base material sheet for adhesive sheets was obtained according to Example 1. FIG. Table 1 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  A polyolefin resin (C) shown in Example 5 of Table 1 was used to obtain a polyolefin resin pressure-sensitive adhesive base sheet according to Example 1. In Example 5, when the film was stretched in the transverse direction, there were many breaks in the stretching under the condition of a stretching ratio of 3 times, so that the base sheet for an adhesive sheet was stretched at a stretching ratio of 2.5 times. Table 1 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

(Comparative Example 1)
In place of the polyolefin resin (C), a polyolefin resin shown in Comparative Example 1 in Table 1 was used to obtain a base sheet for an adhesive sheet according to Example 1. Table 1 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

(Comparative Example 2)
Using the polyolefin resin (C) shown in Comparative Example 2 in Table 1, a base sheet for an adhesive sheet was prepared according to Example 1. In Comparative Example 2, during stretching in the transverse direction, stretching breakage occurred at a draw ratio of less than 1.5 times, resulting in poor stretchability. As a result, no characteristics were obtained.

  A base sheet for an adhesive sheet was obtained in the same manner as in Example 4 except that the lip clearance of the die was adjusted to 1.2 mm in the film forming step. Table 2 shows the stretchability of the film-like molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  A base sheet for an adhesive sheet was obtained in the same manner as in Example 4 except that the lip clearance of the die was adjusted to 2.4 mm in the film forming step. Table 2 shows the stretchability of the film-like molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

(Comparative Example 3)
A base sheet for an adhesive sheet was obtained in the same manner as in Example 4 except that the lip clearance of the die was adjusted to 4.0 mm in the film forming step. Table 2 shows the stretchability of the film-like molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  A base material sheet for pressure-sensitive adhesive sheets was obtained in the same manner as in Example 4 except that the transverse stretching ratio was 5 times and the longitudinal stretching ratio was 6 times. Table 2 shows the stretchability of the film-like molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  A base sheet for an adhesive sheet was obtained according to Example 4 except that the transverse stretching temperature was 80 ° C. Table 2 shows the stretchability of the film-like molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

(Comparative Example 4)
A base sheet for pressure-sensitive adhesive sheets was obtained according to Example 4 except that the transverse stretching temperature was 120 ° C. Table 2 shows the stretchability of the film-like molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  The base material sheet for pressure-sensitive adhesive sheets was obtained in the same manner as in Example 4 except that the stretching in the vertical direction was not performed and only the stretching in the horizontal direction was performed. Table 2 shows the stretchability of the film-like molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

    Performed in the same manner as in Example 1 except that the polyolefin resin (C) shown in Example 11 of Table 3 was used so that the lip clearance of the T die was adjusted to 0.8 mm and the longitudinal stretching temperature was set to 80 ° C. did. Table 3 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  Except having used polyolefin resin (C) shown in Example 12 of Table 3, the base material sheet for adhesive sheets was obtained according to Example 11. FIG. In Example 11, when the film was stretched in the transverse direction, breakage of stretching occurred frequently under the condition of a stretching ratio of 3 times, so that the base sheet for an adhesive sheet was stretched at a stretching ratio of 2.5 times. Table 3 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  Except having used polyolefin resin (C) shown in Example 13 of Table 3, the base material sheet for adhesive sheets was obtained according to Example 11. FIG. Table 3 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  Except having used polyolefin resin (C) shown in Example 14 of Table 3, the base material sheet for adhesive sheets was obtained according to Example 11. FIG. Table 3 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  A base sheet for an adhesive sheet was obtained in the same manner as in Example 11 except that the lip clearance of the T die was set to 0.4 mm in the film forming step. Table 4 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  A base material sheet for an adhesive sheet was obtained in the same manner as in Example 11 except that the lip clearance of the T die was 2.4 mm in the film forming step. Table 4 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  The base material sheet for pressure-sensitive adhesive sheets was obtained in the same manner as in Example 11 except that the stretching in the vertical direction was not performed and only the stretching in the horizontal direction was performed. Table 4 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

  According to Example 11, except that in the stretching step, the first stage stretching was stretched 3 times in the longitudinal direction at a stretching temperature of 23 ° C., and the second stage stretching was stretched 3 times in the transverse direction at a stretching temperature of 80 ° C. Thus, a base sheet for an adhesive sheet was obtained. Table 4 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

(Comparative Example 5)
A base material sheet for an adhesive sheet was obtained in the same manner as in Example 11 except that the lip clearance of the T die was set to 4.0 mm in the film forming step. Table 4 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

(Comparative Example 6)
In the film forming step, a base sheet for an adhesive sheet was obtained in the same manner as in Example 12 except that the temperature of the cooling roll was set to 30 ° C. However, the film was stretched at a draw ratio of 2.5 because breakage occurred frequently under the condition of a draw ratio of 3 times. Table 4 shows the stretchability of the film-shaped molded product and the properties of the base sheet for the pressure-sensitive adhesive sheet.

(Comparative Example 7)
As a commercially available base material sheet for pressure-sensitive adhesive sheets, the properties of the base material sheet for pressure-sensitive adhesive sheets were evaluated by the above method for a polyester resin film having a thickness of 50 μm. Result.

(Table 1)

(Table 2)

(Table 3)

(Table 4)

  Since the base sheet for the pressure-sensitive adhesive sheet of the present invention has high air permeability and can prevent the generation of air bubbles generated when being bonded to an adherend, it is possible to reduce the burden of bonding work, such as a label and a seal It is suitable for a base material sheet for an adhesive sheet.

Claims (18)

A resin composition containing a polyolefin resin (C) composed of crystalline polypropylene (A) and a propylene-α-olefin copolymer (B) dispersed in the crystalline polypropylene (A) is melted and kneaded to form a film. A base sheet for an adhesive sheet formed by forming a film-shaped melt, forming the film-shaped melt into a film-shaped molded product, and then stretching the film-shaped molded product in at least one direction. C) is composed of 30 to 90% by weight of crystalline polypropylene (A) and 10 to 70% by weight of propylene-α-olefin copolymer (B), and communicates with the propylene-α-olefin copolymer (B) region. A base sheet for pressure-sensitive adhesive sheets having fine pores. The melt flow rate ratio MFR _PP / MFR _RC of the melt flow rate MFR _PP of the crystalline polypropylene (A) and the melt flow rate MFR _RC of the propylene-α-olefin copolymer (B) is 0.1 to 10. The base material sheet for pressure-sensitive adhesive sheets according to claim 1, wherein The base material sheet for pressure-sensitive adhesive sheets according to claim 2, wherein the melt flow rate ratio MFR _PP / MFR _RC is 0.2 to 5. The base sheet for pressure-sensitive adhesive sheets according to any one of claims 1 to 3, wherein a draft ratio when the film-shaped melt is formed into a film-shaped molded product is in the range of 1 to 10. The base sheet for an adhesive sheet according to any one of claims 1 to 3, wherein a draft ratio when the film-shaped melt is formed into a film-shaped molded product is in a range of 1 to 3. The polyolefin resin (C) is composed of 40 to 70% by weight of crystalline polypropylene (A) and 30 to 60% by weight of a polypropylene-α-olefin copolymer (B). The base material sheet for adhesive sheets of 1 item | term. The base sheet for pressure-sensitive adhesive sheets according to any one of claims 1 to 6, wherein the propylene content of the propylene-α-olefin copolymer (B) is 30 to 80% by weight. The base material sheet for pressure-sensitive adhesive sheets according to any one of claims 1 to 6, wherein the propylene content of the propylene-α-olefin copolymer (B) is 40 to 70% by weight. The polyolefin resin (C) is obtained by a multistage polymerization method including the steps of producing a crystalline polypropylene (A) in the first stage and continuously producing a propylene-α-olefin copolymer (B) in the second stage. The base material sheet for adhesive sheets of any one of Claims 1-8 characterized by the above-mentioned. Air permeability resistance (Gurley) is 1-2000 second / 100ml, The base material sheet for adhesive sheets of any one of Claims 1-9 characterized by the above-mentioned. The polyolefin resin (C) is composed of 30 to 70% by weight of the crystalline polypropylene (A) and 30 to 70% by weight of the propylene-α-olefin copolymer (B), and has a melt flow rate of the crystalline polypropylene (A). and MFR _PP, when propylene -α- olefin copolymer melt flow rate (B) was _{MFR RC,} claim 1, wherein the ratio _MFR PP / _{MFR RC} melt flow rate is greater than 10 1,000 Base sheet for adhesive sheet. The base sheet for pressure-sensitive adhesive sheets according to claim 11, wherein a draft ratio when the film-shaped melt is formed into a film-shaped molded product is in the range of 1 to 10. The base sheet for pressure-sensitive adhesive sheets according to claim 11, wherein a draft ratio when the film-shaped melt is formed into a film-shaped molded product is in the range of 1 to 5. The base material sheet for pressure-sensitive adhesive sheets according to any one of claims 11 to 13, wherein the propylene content of the propylene-α-olefin copolymer (B) is 30 to 80% by weight. The base material sheet for pressure-sensitive adhesive sheets according to any one of claims 11 to 13, wherein the propylene content of the propylene-α-olefin copolymer (B) is 40 to 70% by weight. The polyolefin resin (C) is obtained by a multistage polymerization method including the steps of producing a crystalline polypropylene (A) in the first stage and continuously producing a propylene-α-olefin copolymer (B) in the second stage. The base material sheet for adhesive sheets of any one of Claims 11-15 characterized by the above-mentioned. Air permeability resistance (Gurley) is 1-2000 second / 100ml, The base material sheet for adhesive sheets of any one of Claims 11-16 characterized by the above-mentioned. A pressure-sensitive adhesive sheet obtained by using the base sheet for pressure-sensitive adhesive sheets according to claim 1 as a surface sheet and laminating a pressure-sensitive adhesive layer.