JPH0240253B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to a method for producing a porous sheet that has excellent tensile strength, tear strength, and dimensional stability, as well as flexibility and moisture permeability (air permeability). For more information,
Crystalline polyolefin, certain ethylene and other α
The present invention provides a method for producing a porous sheet in which a sheet of a composition comprising a copolymer with olefin, an inorganic filler, and a polyester or epoxy plasticizer is stretched under specific conditions. (Prior art and its problems) Conventionally, as a method for manufacturing a porous sheet, a method is known in which an inorganic filler is mixed into a polyolefin resin such as polypropylene or polyethylene, the resulting sheet is formed, and then stretched. Recently, consideration has been given to using such porous sheets in fields such as simple clothing by imparting flexibility to them. A method for imparting flexibility to a porous sheet is generally to mix a linear low-density polyethylene resin into the resin described above. However, such methods have the problem that when uniaxially stretched, the anisotropic physical properties of the resulting stretched sheet deteriorate, particularly the tear strength in the longitudinal (stretching) direction.
Furthermore, biaxially stretched sheets had problems in stretchability and surface strength. In order to prevent this, for example, a method of stretching a sheet of the resin composition as described above at the lowest possible magnification, a method of adding a large amount of liquid softener, a method of adding an inorganic filler to the matrix of the thermoplastic elastomer, etc. However, even with these methods, it has not been possible to obtain a porous sheet that satisfies all of the various properties such as flexibility, moisture permeability, and tensile/tear strength. (Means for Solving the Problems) As a result of various studies regarding the above problems, the present inventors have developed a sheet-like composition of a polyolefin resin, an inorganic filler, a plasticizer, and a resin having a specific density and crystallinity. The inventors have discovered that a porous sheet with excellent flexibility, moisture permeability (air permeability), dimensional stability, tensile/tear strength, etc. can be obtained by stretching the polyester resin, and have proposed the present invention. That is, the present invention provides: (a) 100 parts by weight of a crystalline polyolefin resin, and 20 to 20 parts by weight of a copolymer of ethylene and other α-olefin having a crystallinity of 5 to 25% and a density of 0.86 to 0.90 g/cm ^{3 .} 100 parts by weight of a mixed resin composition (b) 50 to 400 parts by weight of an inorganic filler (c) at least one plasticizer selected from polyester plasticizers and epoxy plasticizers
A sheet-like product obtained by melt-molding a composition formed by blending 0.1 to 20 parts by weight of the above (a), (b) and (c) is heated to 1.3 parts by weight at a temperature below the melting point of the above crystalline polyolefin resin. ~4
This is a method for producing a porous sheet, which is characterized in that it is uniaxially or biaxially stretched at a stretching ratio of 2 times, and then heat-set at the same temperature. In the present invention, first, ethylene and ^other α-
It is extremely important to form a mixed resin composition by blending 20 to 100 parts by weight of a copolymer with olefin in order to obtain a porous sheet with excellent flexibility, moisture permeability, strength, and dimensional stability. be. As the above-mentioned crystalline polyolefin resin, homopolymers or copolymers of olefins such as ethylene and propylene with a degree of crystallinity of 40% or more are generally used without particular restriction, but among them, high-density polyethylene, medium-density polyethylene , medium/low-pressure polyethylene called linear low-density polyethylene,
By using a copolymer of ethylene and other α-olefins, a crystalline propylene homopolymer, or a block copolymer of propylene and other α-olefins, the tensile strength of the resulting porous sheet,
It is preferable because it has excellent tear strength, and linear low-density polyethylene is particularly preferably used. Also, crystallinity 5-25% and density 0.86-0.9
^Copolymers of ethylene and other α-olefins with a carbon content of 86 to 94 mol% are generally random copolymers of ethylene with an ethylene content of 86 to 94 mol% and an α-olefin with a carbon number of 4 to 7 (particularly budene-1). When combined, crystallinity is 5 to 25
%, density 0.86-0.9g/ ^cm3 according to ASTM D-1505
In addition, soft resins (hereinafter simply referred to as soft resins) have properties intermediate between rubbery polymers and crystalline plastics, with a melting point (MP) of 60 to 100°C by differential scanning calorimetry (DSC) and a hardness of 20 to 40 by Shore D. It is called a soft resin). In addition, in the present invention, the crystallinity is
Measured by line diffraction. Therefore, the soft resin of the present invention is an ethylene copolymer generally having an ethylene content of 95 mol% or more, such as the above-mentioned crystalline polyolefin resin, with a density of 0.91 to 0.94, a degree of crystallinity of 40 to 70%, and an M. P=115~130℃, hardness 50~62
This is completely different from linear low density polyethylene. Note that if the density of the soft resin is less than 0.86 g/cm ³ or the degree of crystallinity is less than 5%, the tensile strength and moisture permeability of the obtained stretched sheet will decrease. Furthermore, if the density exceeds 0.9 g/cm ³ or the crystallinity exceeds 25%, the resulting stretched sheet will have reduced flexibility. Furthermore, the soft resin of the present invention preferably has a melt flow index (MFI) of 0.1 to 30 g/10 min at 190°C from the viewpoint of improving the formability and mechanical properties of the stretched sheet; g/10
If it is less than 30 g/min, the melt viscosity is high and the moldability is poor.
If the time exceeds 10 minutes, the melt viscosity will be low, the moldability will be poor, and the tensile strength of the resulting sheet will also be low. The soft resin of the present invention needs to be blended in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of the crystalline polyolefin resin, and if it is less than 20 parts by weight, a porous sheet with the desired flexibility cannot be obtained. First, if the amount exceeds 100 parts by weight, moisture permeability will be significantly reduced when heat setting is performed to impart dimensional stability after stretching, making it impossible to obtain a porous sheet with the desired high moisture permeability. Inorganic fillers that can be applied to the present invention include fillers that are usually mixed into rubber or plastics, such as
Calcium carbonate, gypsum, calcium sulfite, calcium phosphate, magnesium carbonate, basic magnesium carbonate, magnesium sulfate, hydrated silicic acid, anhydrous silicic acid, soda ash, sodium chloride, barium sulfate, clay, various cements, volcanic ash, shirasu, titanium oxide , iron oxide, carbon black, various metal powders, other inorganic substances or organic metal salts mainly composed of inorganic substances, and generally have an average particle size of 500μ or less, preferably in the range of 0.05 to 300μ, particularly about 0.1 to 50μ. It has a diameter. If an inorganic filler with a particle size that is too large is used, the density of the pores in the resulting stretched sheet will decrease, and if an inorganic filler with an average particle size that is too small is used, stretching unevenness will occur during stretching. This tends to occur, making it impossible to obtain the desired porous sheet. The blending ratio of the inorganic filler is 100% of the mixed resin composition of crystalline polyolefin resin and soft resin.
50 to 400 parts by weight, preferably 60 parts by weight
~300 parts by weight; if it is less than 50 parts by weight, a porous sheet with the desired pores cannot be obtained;
If it exceeds 400 parts by weight, it is difficult to form it into a sheet-like product. The polyester plasticizer used in the present invention is
Consists of dibasic or tribasic acids such as sebacic acid, adipic acid, phthalic acid, azelaic acid and trimellitic acid, and ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, long chain alkylene glycol, etc. Among polyester compounds, particularly polyester compounds composed of adipic acid or sebacic acid and propylene glycol, butylene glycol or long-chain alkylene glycol are preferably used. Further, as the epoxy plasticizer, epoxidized oils such as epoxidized soybean oil and epoxidized linseed oil, epoxidized fatty acid esters, liquid epoxy resins, etc. are used. These plasticizers can be used alone or in combination, but in any case, the amount is 0.1 to 20 parts by weight based on 100 parts by weight of the above-mentioned mixed resin composition of crystalline polyolefin resin and soft resin. , preferably 1 to 10
Blend in parts by weight. If the above-mentioned amount is less than 0.1 part by weight, the filler will be poorly dispersed, leading to stretching breakage, and the film will have poor uniform whitening properties, causing uneven stretching. On the other hand, if it is higher than 20 parts by weight, non-uniform flow will occur during the extrusion process to form a sheet, resulting in a decrease in thickness accuracy. The above-mentioned resin composition is generally prepared by mixing powder and granular materials using a blender or the like and then kneading them using an extruder, or by pre-mixing them using a Banbury mixer or other melt kneading machine.
Sheeting is carried out with or without pelletizing.
In such a process, a small amount of lubricant such as liquid paraffin, polyethylene wax, higher fatty acid,
Fatty acid amides, metal soaps, etc., or pigments,
Stabilizers against heat and light, antistatic agents, etc. can be mixed simultaneously or separately. The method of forming the sheet into a sheet is not particularly limited, and extrusion using a circular die or a tape die is generally preferred. In the present invention, it is important to stretch the sheet material at a temperature below the melting point of the crystalline polyolefin resin and then heat set it at that temperature in order to produce the desired porous sheet. In particular, after uniaxially or biaxially stretching at a stretching ratio of 1.3 to 4 times at a temperature below the softening point of the copolymer of ethylene and other α-olefins, heat setting is performed at a temperature below the melting point of the crystalline polyolefin resin. The sheet obtained by this method is preferable because it has excellent physical properties such as moisture permeability. This is presumed to be because the degree of porosity due to stretching differs at the softening point of the soft resin, and is thought to be because favorable physical properties as a sheet occur under the above conditions. The stretching in the present invention is carried out uniaxially or biaxially at a stretching ratio of 1.3 to 4 times. That is, the stretching ratio is
When the stretching ratio is less than 1.3 times, stretching unevenness occurs during stretching, and on the other hand, when the stretching ratio exceeds 4 times, stretching breakage of the sheet occurs. In addition, heat setting methods generally include a method in which the sheet is brought into contact with a heated roll with or without holding the edges, and a method in which the sheet is passed through a heated oven, and the heat setting time is set so as to obtain the desired dimensional stability. In addition, it should be determined based on the relationship between sheet feeding speed and temperature. (Effect) The porous sheet obtained by the present invention has a thickness of
0.01~1.0mm, preferably 0.02~0.5mm, porosity 20
~55%, moisture permeability 1500~3000g/ ^m2・24HrS, tensile strength at break 30~210Kg/ ^cm2 , elongation 150~900%, tear strength 13~100g, flexibility, moisture permeability, strength, water repellency and Due to its excellent dimensional stability, it is used for applications such as simple clothing, sanitary materials, and breathable packaging materials. (Example) Examples will be shown below, and the physical properties thereof were measured by the method shown below. (1) Porosity: Calculated from the density of the sheet based on the following formula. Porosity (%) = ρ ₀ - ρ / ρ ₀ ×100 ρ ₀ : Density of sheet before stretching (g/cm ³ ) ρ : Density of sheet after stretching (g/cm ³ ) (2) Tensile strength at break and elongation: Tensilon (manufactured by Toyo Baldwin) at a speed of 200 mm/min. Measured with dumbbell No. 1 (3) Tear strength: JIS L1085 AI Measured sample 4cm width x 15cm length (4) in accordance with the single tongue method Moisture permeability: JIS Z0208 at 25℃ and 90% relative humidity
Measured in accordance with (5) Flexibility: Judging by the feel of the hand according to the following criteria A: Very soft B: Soft C: Examples 1 to 15 lacking in softness Resin, in the proportions shown in Table 1. An inorganic filler and a plasticizer were mixed and used. Specifically, in a 20 hexyl mixer, a polyester plasticizer and an epoxy plasticizer are added to the inorganic filler alone or as a mixture with stirring, and then the crystalline polyolefin resin and the soft resin are dispersed and mixed. did. 10 kg of the obtained resin composition was transferred to a CCM kneading extruder (Chuo Kikai Co., Ltd.).
After granulation using a CCM-50 model manufactured by Co., Ltd., it was dried at 100°C for 2 days. Next, the blowing ratio was adjusted using a 50 m/mφ extruder with a circular die of 150 m/m in diameter.
2.0, a raw sheet with a thickness of 65 μm and a fold diameter of 470 m/m was wound up. Next, the sheet is passed through a roll stretching machine at a speed of 15 to 30 m/min on the high speed side, as shown in Table 2.
The sheet was stretched under the conditions shown below, heat-set by passing through an oven having guide rolls at a speed of 15 to 30 m/min, and then slit at both ends and wound up. The physical properties of the obtained porous film are shown in Table 2.

【table】

【table】

【table】

[Stretching and heat setting conditions]

Roll stretching temperature 40℃ (Comparative example -8, 50℃) 〃 Magnification 1.3~5.0x 〃 Speed 13~50m/min (High speed side)

【table】

【table】

[Table] Oven heat setting Temperature: 100°C Speed: 13 to 20 m/min Time: 15 to 23 seconds *1 to *3 Method for producing ethylene-butene-1 copolymer as a solvent
EDC was continuously supplied at a rate of 500 ml per hour, and the polymerization solution was drawn out from the bottom of the polymerization vessel so that the volume was always 500 ml. As a catalyst, (A) a reaction product of vanadium oxytrichloride and cyclohexanone (molar ratio = 1/3) 0.3 mol/(B) ethylaluminum sesquichloride 6 mol/ is added dropwise to the polymerization vessel at a constant rate. Also, a mixed gas of ethylene and 1-butene (90 mol of ethylene
%, 1-butene 10 mol%) at a rate of 300/hr,
Polymerization was carried out at a temperature of 20° C. while supplying hydrogen gas as a molecular weight regulator at a rate of 10/hr. After stopping the reaction with a small amount of methanol in the polymerization liquid taken out from the bottom of the polymerization vessel, the polymer was separated, further washed with methanol, and dried under reduced pressure at 50°C overnight to obtain 100 g of white powdery copolymer. Obtained at a rate of hr. When this product was measured by infrared spectrum analysis, the ethylene content of the copolymer was 87.0 mol%, the melt flow index (190°C/10 minutes) was 2.3, and the density was 0.89.
g/cm ³ Crystallinity measured by X-ray diffraction: 16.0%,
The Vicat softening point according to ASTM D-1525 was 60°C. (*2) Ethylene-butene-1 copolymers having the properties *1 and *3 shown in Tables 1 and 3 were produced by changing the reaction conditions in the same manner.

Claims (1)

[Claims] 1 (a) 100 parts by weight of crystalline polyolefin resin,
Crystallinity 5-25% and density 0.86-0.9g/ ^cm3
100 parts by weight of a mixed resin composition prepared by blending 20 to 100 parts by weight of a copolymer of ethylene and other α-olefins (b) 50 to 400 parts by weight of an inorganic filler (c) a polyester plasticizer and At least one plasticizer selected from epoxy plasticizers
A sheet of the composition consisting of 0.1 to 20 parts by weight of the above (a), (b) and (c) is uniaxially stretched at a temperature below the melting point of the crystalline polyolefin resin described above at a stretching ratio of 1.3 to 4 times. Alternatively, a method for producing a porous sheet, which comprises biaxially stretching and then heat-setting at the same temperature.