JP5600835B2 - Method for manufacturing moisture permeable waterproof sheet - Google Patents

Description

  The present invention relates to a moisture permeable waterproof sheet.

Conventionally, asphalt felt, asphalt roofing, and the like are commercially available as waterproof sheets, but these are waterproof, but they are not moisture permeable or their degree is extremely low. When there is a large temperature difference in the water vapor, water vapor and water droplets may be generated, the inside may condense, and the contacting support may be damaged. Moreover, since the thing currently used has impregnated or apply | coated the asphalt to paper or a nonwoven fabric, there existed a problem that weight was large, handling property was bad, and workability | operativity also worsened (refer patent document 1).
Therefore, by using a polyolefin resin foam excellent in flexibility, it has excellent waterproof properties and excellent moisture permeability. Furthermore, by using a polyolefin resin foam, performance was maintained even in harsh usage environments, and weight problems were solved.
However, although there are descriptions of various physical properties and improvement points in the patent documents so far, there is no description about a specific manufacturing method or one using a foam (Patent Documents 2 and 3). reference).

JP 10-280623 A JP2007-126953 Patent No. 4021524

  The objective of this invention is providing the moisture-permeable waterproof sheet characterized by moisture permeability and waterproofness.

  The inventor has intensively studied to achieve the above-described problems. As a result, it is obtained by supplying a specific thermoplastic resin composition to an extruder, press-fitting carbon dioxide into the extruder as a foaming agent, kneading with a molten resin, and then extruding and foaming at a specific discharge speed and pressure. It has been found that the above-described problems can be achieved by a foam in which the foam cross-section is exposed on both sides of the foam by performing a secondary process of cutting or cutting both sides of the foam.

The present invention provides the following moisture-permeable waterproof sheets.
1 A moisture-permeable waterproof sheet characterized by being in a state in which a cell cross section is exposed on both surfaces of a foam by performing a secondary process of cutting or cutting both surfaces of a polyolefin resin foam.
2 A moisture permeable waterproof sheet obtained by mixing a thermoplastic elastomer into a polyolefin resin foam.
3. A moisture permeable waterproof sheet, wherein the polyolefin resin foam has a moisture permeability of 10 to 500 g / m ² · h and a water resistance of at least 200 mmH ₂ O.
4 A moisture-permeable waterproof sheet, wherein the polyolefin resin foam has an average cell diameter in the range of 0.02 to 0.2 mm.
5 A moisture-permeable waterproof sheet, wherein the polyolefin resin foam has a thickness in the range of 0.5 to 2.0 mm and an apparent density in the range of 35 to 100 kg / m ³ .
6 A moisture-permeable waterproof sheet, wherein a base material made of a woven fabric, a knitted fabric or a non-woven fabric is laminated on at least one surface of a polyolefin resin foam.

According to the present invention, the following remarkable effects can be obtained.
(1) The moisture permeable waterproof sheet of the present invention is a polyolefin resin foam in which a thermoplastic elastomer is contained in a predetermined proportion in a polyolefin resin having a predetermined melt flow rate, and therefore has low crystallinity. Elastomer relaxes the temperature dependence of melt viscosity in polyolefin resin, widens the appropriate foaming temperature to improve foamability, uses carbon dioxide as a foaming agent, and further creates a bubble generation part and a foam molding part. A foam with good surface smoothness is obtained by using an annular die having extrusion foaming at a predetermined discharge speed and pressure, thereby reducing the size of the bubbles, improving the strength of the bubble film, and improving the expansion ratio. It becomes possible.
(2) In the present invention, by using the above method, fine bubbles can be formed, the foaming ratio is high, the cushioning property and flexibility are excellent, and the surface is less uneven and wrinkled. Since an excellent polyolefin resin foam can be produced stably and continuously, it is excellent in slicing process for removing the skin on both sides of the foam by having excellent surface smoothness.
(3) The moisture-permeable waterproof sheet obtained by the present invention has excellent waterproof properties that do not allow water to pass through, and also has a feature of allowing water vapor and air to permeate. Conditions that involve movement of moisture and air, such as moisture / waterproof materials, moisture permeable waterproof sheets around bathtubs, nursing permeable waterproof sheets, moisture permeable waterproof sheets for electronic devices or electronic device components, etc. It can be suitably used when used below.

  Conventionally, the materials used for wall surfaces of general houses, roofing materials, etc. are waterproof, but do not have moisture permeability, or the moisture permeability is extremely small, so the temperature difference between indoors and outdoors is large. In this case, there is a first problem that water vapor generated inside these sheets may condense or wrinkles may damage the support in contact with the sheets.

  In addition, sheets used as roof coverings and house wraps generally use tucker, nails, etc. to fix them, and since there are gaps and holes at that time, rainwater that has infiltrated from the tiles and outer walls can be removed. There was a second problem of passing through the gaps and holes and damaging the support.

  In order to solve the second problem, a sheet provided with a water-expandable colloidal clay layer (Japanese Utility Model Laid-Open No. 5-61074) or a method of fixing a superabsorbent polymer having a high water absorption ratio using a binder (Japanese Patent Laid-Open No. 7-1990). No. 279054) has been developed, however, there are problems such that the moisture permeability is inferior due to the thick sheet, and the polymer layer is exposed and swells when in contact with water, making it difficult to handle. At the same time, the third problem occurs such that the weight of the sheet increases and the workability deteriorates.

  In order to solve these problems, by removing both surfaces of the foam having fine bubbles and exposing the fine bubbles, it has an excellent waterproof property that does not allow water to pass through, and allows water and other gases to pass through, as well as water vapor. The first problem can be solved by transmitting the light. Next, generation | occurrence | production of a clearance gap etc. is suppressed by being excellent in a softness | flexibility and cushioning properties, and it becomes possible to maintain further intensity | strength by performing secondary processing or compounding with another member. Furthermore, since it is a foam, it is light in weight and contributes to weight reduction when secondary processing such as bonding is performed. These characteristics not only have an effect on the use of building materials, but also prevent electronic devices from leaking into the cabinet and discharge the gas generated inside, as well as the release of water vapor and gas. It is possible to use suitably for the member etc. which require this.

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

(Manufacturing method of polyolefin resin foam)
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 5 g / 10 min and 10 to 300 parts by weight of a thermoplastic elastomer is supplied to an extruder. Then, after press-fitting carbon dioxide into the extruder as a foaming agent and kneading with the molten resin composition, a method for producing a thermoplastic resin foam that is extruded and foamed from the annular die D shown in FIG. It is.
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 It is characterized by extrusion foaming 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.

  The thermoplastic resin composition used in the present invention contains 100 parts by weight of a polyolefin resin having a melt flow rate of 0.2 to 5 g / 10 min, 10 to 300 parts by weight of a thermoplastic elastomer, and a cell nucleating agent as essential components.

(Polyolefin resin)
The polyolefin resin is not particularly limited as long as the melt flow rate is about 0.2 to 5 g / 10 min. 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, and the like. An α-olefin 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 cross-linking, 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. Therefore, it is limited to about 0.2 to 5 g / 10 min, preferably about 0.2 to 4 g / 10 min, and more preferably about 0.3 to 3.5 g / 10 min.
In this specification, the melt flow rate of polyolefin 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, and 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 / 10 min) = (MFR ₁ ) ^{C 1} × (MFR ₂ ) ^{C 2} × ... × (MFR _n ) ^Cn

(Thermoplastic elastomer)
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 content of the thermoplastic elastomer is small, the resulting polyolefin resin foam has poor buffering properties and flexibility. On the other hand, if the content is large, the rubber elasticity of the thermoplastic resin composition becomes too strong and the foamability is lowered. In order to increase the shrinkage of the obtained polyolefin resin foam, it is limited to about 10 to 300 parts by weight with respect to 100 parts by weight of the polyolefin resin, preferably about 20 to 150 parts by weight, and 30 to 100 parts by weight. About 40 parts by weight is more preferable.

(Bubble nucleating agent)
The thermoplastic resin composition used in the present invention contains a cell nucleating agent. The cell nucleating agent promotes the generation of cell nuclei when the thermoplastic 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 and supplied as a thermoplastic resin composition or separately into the extruder, and further as a masterbatch with the compounded resin composition They may be mixed and supplied as a thermoplastic resin composition or individually into the extruder.
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 thermoplastic resin composition used in the present invention, various additives usually used in 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 pressed into an extruder in order to foam the thermoplastic resin composition, and carbon dioxide is used in the present invention. 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.

  The mold used in the method for producing a polyolefin-based resin foam of the present invention includes the bubble generating part 2 formed by the restriction 31 of the resin flow path 3 and the growth and foaming of the generated bubbles, as shown in FIG. An annular die D having a foam molding part 1 for smoothing the body 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, 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.
Preferably ejection velocity V is approximately 70~250kg / ^cm 2 · hr, and more preferably about 100~200cm ² · hr. The resin pressure before the ring die is 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 workability in the case of secondary processing of the obtained foam is improved. For example, a sheet-like foam obtained by slicing can have a superior 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.

(Polyolefin resin foam)
When the average cell diameter of the polyolefin resin foam obtained by the method of the present invention is small, foam breakage increases, and the apparent density of the polyolefin resin foam may increase. Since the breathability, moisture permeability, water pressure resistance, etc. of the body may be lowered, it is preferably about 0.02 to 0.3 mm, more preferably about 0.05 to 0.2 mm. A thickness of about 07 to 0.18 mm is particularly preferable.

(Laminated substrate)
As a laminate base material used in the present invention, a woven fabric, a knitted fabric or a non-woven fabric composed of cellulose fibers such as cotton, viscose rayon, and pulp, and synthetic fibers such as polyester, polyamide, polypropylene, polyvinyl alcohol, and acrylic. Is mentioned. Among these, polypropylene is preferable because of its excellent heat processability.
Laminating a base material made of woven fabric, knitted fabric or non-woven fabric maintains the air permeable, moisture permeable or waterproof function, and also improves the strength, thereby improving workability, wall surface, roofing It can use suitably for a member etc.

[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.
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
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. because, is preferably in the range of about 35~100kg / ^{m 3,} more preferably in the range of about 35~90kg / ^{m 3,} particularly that in the range of about 40~70kg / ^{m 3} preferable.

(Water pressure resistance)
In this specification, the water pressure resistance of the polyolefin resin foam is measured by a method based on the method described in the JIS L1092 A method. Specifically, five test pieces of about 150 mm × 150 mm are collected, attached to the apparatus so that the front side of the test piece is in contact with water, and the water level is increased at a predetermined speed by adding a water-filled level device. Measure the water level in mm when water comes out from three places on the back side of. As the measuring device, a water resistance tester commercially available from Yasuda Seiki Seisakusho can be used.
Water pressure of the polyolefin resin foam is a 100 mm H ₂ O or less, because at the same time water droplets when applying a water pressure is generated, preferably at 200 mm ₂ O or more, more preferably 300mmH ₂ O or more, 400MmH ₂ Most preferably, it is O or more. The upper limit is not particularly limited, and the higher the better, but it is naturally limited by the measurement method.

(Moisture permeability)
In the present specification, the moisture permeability of the polyolefin resin foam is measured by a method based on the method described in JIS L1099 A-1 calcium chloride method. Specifically, about 33 g of a hygroscopic agent is put in a moisture permeable cup preheated to about 40 ° C., and the cup is vibrated and made uniform, and then the surface is flattened and a hygroscopic agent is tested using a circular plate. Adjust so that the distance from the lower surface of the piece is 3 mm.
Next, place the surface of the Φ70 test piece facing the moisture absorbent side so as to be concentric with the moisture permeable cup, install the packing and ring in order, fix it with a nut, and then use vinyl adhesive tape to attach the mounting side. Seal the specimen. This specimen is placed at a position where the wind speed of about 1 cm above the specimen in a constant temperature / humidity apparatus having a temperature of 40 ± 2 degrees and a humidity of 90 ± 5% RH does not exceed 0.8 m / s.
The test specimen is taken out after 1 hour and the mass is immediately measured to 1 mg. After the measurement, the test specimen is placed again at the same position on the thermostatic / humidity device, and the test specimen is taken out after 1 hour, and the mass is immediately measured to 1 mg. As a measuring device, a low-temperature constant temperature and humidity chamber HPAV-120-20 commercially available from ISUZU Seisakusho can be used.
If the moisture permeability of polyolefin resin foam is small, not only does water not pass when it is desired to evaporate only water vapor, it restricts the movement of water vapor, making it suitable for use under conditions involving moisture movement. On the other hand, if it is large, not only water vapor but also water may be passed, so the water vapor transmission rate is preferably in the range of about 10 to 500 g / m ² · h, and 15 to 450 g. / ^m is more preferably in the range of about ² · h, particularly preferably in the range of about 20 to 400 g / ^{m 2} · h.

(Gurley air resistance)
In the present specification, the air resistance of the polyolefin resin foam is measured by a method based on the method described in JIS P8117-1998. Specifically, air is compressed by the vertical weight of the inner cylinder floating on the liquid surface, this air passes through the test piece, the inner cylinder descends gradually, and it is necessary for a certain volume of air to pass through. Measure the elapsed time. As a measuring device, the Gurley tester B type marketed by Toyo Seiki Seisakusho can be used.
If the air resistance of the polyolefin resin foam is small, the bubble diameter is coarse, the physical properties such as flexibility may be inferior, and water may be passed through instead of water vapor. In addition, since air bubbles are coarse, fine powder or the like may leak, and thus the air resistance is preferably 0.3 seconds or more.

(Tensile test)
In the present specification, the maximum tensile stress and tensile elongation of the polyolefin resin foam are measured by a method based on the method described in JIS K 6251. Specifically, a dumbbell-shaped No. 3 test piece punched in the tensile direction in the MD direction and the width direction (direction perpendicular to the tensile direction) in the MD direction with a tensile tester having a gripper or pulley that moves at a constant speed. Measure the maximum tensile force and elongation during continuous pulling or when cutting. As a measuring device, a Tensilon universal testing machine marketed by Orientec Co., Ltd. can be used.

(Tear test)
In the present specification, the tear strength of the polyolefin resin foam is measured by a method based on the method described in JIS K 6767. Specifically, the test piece described in JIS K 6767 is continuously pulled until the test piece is cut with a tensile tester having a gripper or pulley that moves at a constant speed, and the maximum load at the time of cutting is measured. The MD direction is the tear direction, and the TD direction is the width direction (the direction perpendicular to the tear direction). As a measuring device, a Tensilon universal testing machine marketed by Orientec Co., Ltd. can be used.

  The obtained polyolefin resin foam can be removed by slicing the skin. The polyolefin-based resin foam obtained in the present invention is excellent in slicing workability, and by removing the skin of the foam, it has excellent air permeability and moisture permeability, and there is little occurrence of creases even when bent. Furthermore, it becomes a foam excellent in surface smoothness, flexibility and buffering property. As the slicing machine, a known machine such as a machine with a rotating blade can be used.

  By laminating a polyolefin resin foam from which the skin has been removed and a woven, knitted or non-woven fabric, etc., while maintaining the functions of air permeability, moisture permeability or waterproofness, it also has excellent physical properties such as tensile strength or tear strength. Foam. As a laminating method, a known method such as a mesh fusion or hot air fusion can be used.

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 a polyolefin-based resin (Newstor SH9000 MFR: 0.3 g / 10 min manufactured by Nippon Polypro Co., Ltd.) is heated to a heat which is an uncrosslinked ethylene-propylene-diene copolymer elastomer. A masterbatch containing 70% by weight of talc having an average particle size 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 a plastic elastomer (Thermolan Z101N MFR: 14 g / 10 min manufactured by Mitsubishi Chemical Corporation) The thermoplastic resin composition in which 10 parts by weight of Talpet Talpet 70P) was mixed 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. Then, the bubble generating part diameter Φ35 mm of the mold attached to the tip of the second extruder, the bubble generating part interval of the mold 0.25 mm (cross-sectional area of the bubble generating part: 0.275 cm ² ), the interval of the foam molding part Discharge rate 30 kg / hr (discharge rate V = 109 kg / cm ² · hr), resin temperature 175 ° 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 polyolefin resin foam. Both sides of the obtained polyolefin resin foam were sliced by a splitting machine (“AB-320D” manufactured by Fortuna Co.) to remove the epidermis, and a sheet-like foam having a thickness of 1.0 mm and a sliced surface was obtained. Obtained.

(Example 2)
In the same manner as in Example 1, except that the thermoplastic elastomer was changed to Exlink 3300B (MFR: 0.9 g / 10 min) manufactured by JSR, which is a non-crosslinked ethylene-propylene-diene copolymer elastomer, supercritical dioxide dioxide Carbon (4.8 parts by weight) was injected and extruded and foamed under the conditions of a resin temperature of 172 ° C. and a resin pressure of 10.8 MPa before the annular die to obtain a polyolefin resin foam. Both sides of the obtained polyolefin resin foam were sliced by a splitting machine (“AB-320D” manufactured by Fortuna Co.) to remove the epidermis, and a sheet-like foam having a thickness of 1.0 mm and a sliced surface was obtained. Obtained.

(Example 3)
4 in the same manner as in Example 1 except that 9 parts by weight of a master batch (MZX-4 manufactured by Mitsubishi Rayon Co., Ltd.) containing 20% by weight of polytetrafluoroethylene as a cell nucleating agent was mixed. .2 parts by weight was injected and extruded and foamed under the conditions of a resin temperature of 176 ° C. and a resin pressure of 10.8 MPa in front of the annular die to obtain a sheet-like polyolefin resin foam. The obtained foam was sliced with a splitting machine (“AB-320D” manufactured by Fortuna) to remove the epidermis, thereby obtaining a sheet-like foam having both sides with a thickness of 1.0 mm as slice surfaces.

Example 4
In the same manner as in Example 2 except that 9 parts by weight of a master batch (MZX-4 manufactured by Mitsubishi Rayon Co., Ltd.) containing 20% by weight of polytetrafluoroethylene as a cell nucleating agent was mixed. .8 parts by weight was injected and extruded and foamed under conditions of a resin temperature of 175 ° C. and a resin pressure before the ring die of 12.1 MPa to obtain a polyolefin resin foam. The obtained foam was sliced with a splitting machine (“AB-320D” manufactured by Fortuna) to remove the epidermis, thereby obtaining a sheet-like foam having both sides with a thickness of 1.0 mm as slice surfaces.

(Example 5)
9 parts by weight of a master batch (MZX-4 manufactured by Mitsubishi Rayon Co., Ltd.) containing 20% by weight of polytetrafluoroethylene as a cell nucleating agent is mixed, and the thermoplastic elastomer is a dynamically crosslinked ethylene-propylene-diene copolymer elastomer. Except for changing to EXSRINK 2700B (MFR: 11 g / 10 min) manufactured by JSR Corporation, 5.3 parts by weight of supercritical carbon dioxide was injected in the same manner as in Example 1, and the resin temperature was 173 ° C. Extrusion foaming was performed under the condition of the front resin pressure of 14.2 MPa to obtain a polyolefin resin foam. The obtained foam was sliced with a splitting machine (“AB-320D” manufactured by Fortuna) to remove the epidermis, thereby obtaining a sheet-like foam having both sides with a thickness of 1.0 mm as slice surfaces.

(Example 6)
A sheet-like foam was obtained by bonding a nonwoven fabric made of polypropylene (6630-1A, manufactured by Shinwa Co., Ltd.) with hot air at a hot air temperature of 380 ° C. and a speed of 8 m / min on both surfaces of the sheet obtained in Example 1.

(Comparative Example 1)
With the foam obtained in Example 1, a sheet-like foam that was not subjected to slicing to remove the skin was prepared.

(Comparative Example 2)
A commercially available polyethylene open-cell foam (Opcell LC-300 # 2D, manufactured by Sanwa Chemical Co., Ltd.) was sliced with a splitting machine (“AB-320D” manufactured by Fortuna) in the same manner as in the examples. Was removed to obtain a foam having a thickness of 1.0 mm and sliced surfaces.

(Comparative Example 3)
A closed cell foam (Softlon made by Sekisui Chemical Co., Ltd.) obtained by irradiating a commercially available polyethylene with an electron beam is sliced by a splitting machine (“AB-320D” made by Fortuna) in the same manner as in the example, and the epidermis is obtained. After removing, a foam having a thickness of 1.0 mm and a sliced surface was obtained.

(Comparative Example 4)
The nonwoven fabric (6630-1A manufactured by Shinwa Co., Ltd.) used in Example 6 was used.

(Physical property test)
About each foam obtained by each Example and the comparative example, the average bubble diameter, the Gurley permeability resistance, the moisture permeability, and the water pressure resistance were measured and compared. The comparison results are shown in the writing.

  Table 1 shows the results of resin discharge speed, density, sheet thickness, Gurley air resistance, moisture permeability, and water pressure resistance for the foams of each example and comparative example. Table 1 shows the results of the maximum tensile stress, the maximum point elongation, and the tear strength for each of the foams of the examples and comparative examples.

In this example, a polyolefin-based resin foam having fine bubbles, having a good foam density and a good sheet thickness and having a beautiful surface is obtained, and secondary processing for cutting or cutting both surfaces of the obtained foam is performed. By applying, a polyolefin resin foam having characteristics of moisture permeability and waterproofness is obtained. In this example, as shown in the table, the moisture permeability is in the range of 10 to 500 g / m ² · h, and the water resistance is preferably at least 200 mmH ₂ O, and the average cell diameter is This also indicates that a range of 0.02 to 0.2 mm is preferable. In Comparative Example 1, a foam having a beautiful surface was obtained. However, since the cell cross section was not exposed, the water pressure resistance was high, but the moisture permeability was small. In Comparative Example 2, the moisture permeability was large, but the water pressure resistance was small and the waterproof property was low. In Comparative Example 3, the water pressure resistance was high and the waterproof property was high, but the moisture permeability was small and water vapor hardly passed.
Further, in this example, even when a nonwoven fabric is laminated on both sides, it is possible to laminate the surface beautifully, and the moisture permeability and waterproof characteristics are maintained even when the lamination is applied. Moreover, the maximum tensile stress, the maximum point elongation, and the tear strength are improved by applying the laminate. In Comparative Example 4, the maximum tensile stress, the maximum point elongation, and the tear strength were the same as in Example 6, and the moisture permeability was large. However, there was no water pressure resistance, the waterproofness was extremely small, and air, water vapor, and water could pass easily.

  The present invention is characterized by having excellent moisture permeability and water pressure resistance and fine bubbles. These properties can be suitably used for use under conditions involving moisture movement, such as use under high temperature or dry conditions. Specifically, it can be used as a moisture permeable waterproof sheet for an electronic device or an electronic device member as a moisture permeable / water proof material used for a building or the like, a moisture permeable waterproof sheet around a bathtub or for nursing care.

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)

Melting and kneading a polypropylene resin and a thermoplastic elastomer, and performing a secondary process of cutting or cutting both sides of a polypropylene resin foam sheet not added with a nonionic surfactant extruded in a sheet form from an annular die , the state der exposing the bubble cross section on both sides of the foam sheet is, the moisture permeability of the resulting polypropylene-based resin foam sheet is in a range of 10~500g / m ² · h, and, water resistance of at least 200mmH moisture permeable waterproof sheet, wherein ₂ O der Rukoto. Moisture permeable waterproof sheet according to claim 1, wherein the average cell diameter of the foamed polypropylene resin sheet and said range der Rukoto of 0.02 to 0.2 mm. In the range of thickness of the foamed polypropylene resin sheet 0.5 to 2.0 mm, and, according to claim 1 or 2 SL placing permeable apparent density, characterized in that in the range of 35~100kg / ^{m 3} Wet tarpaulin. The moisture-permeable waterproof sheet according to any one of claims 1 to 3, wherein a base material made of a woven fabric, a knitted fabric, or a non-woven fabric is laminated on at least one surface of the polypropylene resin foam sheet.

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