JP4231749B2 - Method for producing thermoplastic resin foam having concave grooves - Google Patents

Description

  The present invention relates to a method for producing a thermoplastic resin foam having a concave groove suitable for keeping warm and holding a hot water supply pipe, a linear electric heater and the like.

  In recent years, due to an increase in demand for floor heating, there is an increasing demand for a thermoplastic resin foam having a concave groove for keeping and holding hot water pipes, linear electric heaters and the like. In general, as a method of forming a groove in a thermoplastic resin foam, a method of introducing a resin into a hermetic mold and heat-forming foaming, or obtaining a sheet-like foam and then mechanically cutting the groove There are known methods for providing such.

  However, in the method of heating and foaming with a closed mold, every time the target shape changes, a large mold according to the shape must be prepared, and there is a problem that the cost of the mold is very high, In addition, since a sealed mold is used, there is a problem that a foam having a concave groove cannot be continuously produced. Further, the above cutting method has a problem in productivity.

  Furthermore, there is also a method in which a mold having protrusions with a desired arrangement is pressed on one surface of the foam to continuously form concave grooves corresponding to the protrusions in the foam. In general, the groove formed in the foam has a constant width from the opening to the bottom in the cross-sectional shape, or the width gradually decreases from the opening toward the bottom. When the pipe is laid on the pipe, the force for holding the pipe is weak, and when the external force is applied, the pipe easily comes out. For this reason, the extra work of fixing the laid pipe to the foam with an adhesive tape or the like is required.

  As a method for solving the problem that the above-mentioned pipe easily comes out, for example, in Patent Document 1, a fibrous cushion material is laminated on a base, and a groove forming member is heated on the upper surface of the cushion material. In the method for manufacturing a hot water mat for floor heating, wherein a hot water pipe is formed by pressing to form a pipe storage groove opened upward, a hot water pipe is stored in the pipe storage groove, and a surface layer material is laminated thereon. A cut is formed in advance so as to cut the fiber from the upper surface of the fibrous cushioning material along the piping pattern of the pipe, and then the groove forming member is hot-pressed so as to follow the cut to form a pipe storage groove. A method for manufacturing a hot water mat for floor heating is disclosed.

  However, in recent years, in order to reduce material recyclability and environmental burden, unlike the above-mentioned fibrous cushion material such as a fiber mat, as a thermoplastic resin foam having an improved compression modulus, individual bubbles A resin foam in which a face material having a strength capable of suppressing the foaming force in the in-plane direction generated when heating and foaming is laminated on both surfaces of a polyolefin-based resin foam oriented in the thickness direction is often used. Even with such a resin foam with a face material, there is a need for a method for producing a thermoplastic resin foam in which a ditch can be easily formed and a ditch that can hold a pipe reliably is formed. It was.

  Moreover, in patent document 2, it has the cross-sectional shape by which the tip of the base became the bulging part on one surface of the thermoplastic resin foam from our company, and the height is more than the maximum width of the bulging part. A thermoplastic resin foam having a concave groove, characterized in that a concave groove is formed by heating and pressing a mold provided with a ridge above the melting point of the thermoplastic resin constituting the thermoplastic resin foam. A method for manufacturing a body is disclosed.

  However, when the method described in Patent Document 2 is applied to the resin foam with a face material, depending on the characteristics of the face material, a gentle curvature (R) is easily attached to the opening corner of the groove, and a good groove shape is obtained. There was a problem that could not get.

JP 2002-39556 A JP 2001-219467 A

  In view of the above-mentioned conventional problems, the object of the present invention is a resin foam with a face material having a good compressive strength, which is made of a polyolefin-based material with little environmental load, and is difficult to have a curvature at the opening corner of the groove, It is an object of the present invention to provide a method for producing a thermoplastic resin foam having a concave groove that can be easily molded and can reliably hold a pipe or a linear heater.

The method for producing a thermoplastic resin foam having a concave groove according to claim 1 comprises a non-woven fabric made of polyethylene terephthalate resin on both sides of a polyolefin resin foam in which individual cells are oriented in the thickness direction, and is heated and foamed. A method for producing a thermoplastic resin foam having a concave groove on at least one surface of a resin foam with a face material in which a face material for suppressing foaming force in an in-plane direction is laminated. Heating a mold having a ridge that has a cross-sectional shape with a tip formed as a bulge and whose height is equal to or greater than the maximum width of the bulge so that the mold temperature is 180 to 220 ° C. And after forming a ditch | groove by pressing on the surface of the resin foam with a face material at a pressing speed of 1-2 second / cm, it demolds after cooling.

  The method for producing a thermoplastic resin foam having a recessed groove according to claim 2 is the method for producing a thermoplastic resin foam having a recessed groove according to claim 1, wherein the nonwoven fabric is made of a polyethylene terephthalate resin. The mold temperature is 180 to 220 ° C.

Method for producing a thermoplastic resin foam having a concave groove of the second aspect, a method for producing a thermoplastic resin foam having a concave groove of claim 1 Symbol mounting, the expansion ratio of the polyolefin resin foam It is 3 to 20 times, the average value of the aspect ratio Dz / Dxy of the internal bubbles is 1.1 to 4.0, and the compression elastic modulus is 6 MPa or more.

  The resin foam with a face material is, for example, a foamable polyolefin resin sheet obtained by shaping a foamable polyolefin resin composition kneaded by adding a pyrolytic foaming agent to a polyolefin resin into a sheet shape. The foamable composite sheet having the face material laminated on both sides is obtained by heating to a temperature equal to or higher than the decomposition temperature of the thermally decomposable foaming agent and foaming.

  The resin foam with a face material thus obtained is a two-dimensional in-plane because the face material laminated on both sides of the expandable polyolefin resin sheet suppresses the foaming force in the in-plane direction during foaming. The foam expands only slightly in the direction, and foams only in the thickness direction of the expandable polyolefin resin sheet. As a result, the bubbles constituting the obtained foam have their major axis oriented in the thickness direction. It has a spindle shape, and is arranged like a rugby ball upright in the same direction and aligned horizontally, and is laminated in layers in the thickness direction.

  In the present invention, the in-plane direction refers to a two-dimensional direction defined by the longitudinal direction and the width direction of the polyolefin resin foam, and refers to a direction orthogonal to the thickness direction.

  The polyolefin resin constituting the polyolefin resin foam is not particularly limited, and examples thereof include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, isotactic or syndicate. Tactic homopolypropylene, block propylene copolymer, random propylene copolymer, polybutene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, Examples include ethylene-acrylic acid ester copolymers. These may be used singly or in combination of two or more.

  In the polyolefin-based resin, other thermoplastic resin, for example, a compatible thermoplastic resin such as polystyrene, an elastomer, or the like may be mixed and used within a range of 30% by weight or less.

  The melt flow rate (MFR) of the polyolefin-based resin is preferably measured in accordance with JIS K7210 because it is too low or too low to reduce foaming stability. The value is 0.1 to 20 g / 10 min.

  The polyolefin resin may be cross-linked as necessary. The crosslinking method is not particularly limited. For example, an electron beam crosslinking method in which ionizing radiation such as an electron beam is irradiated, a chemical crosslinking method using an organic peroxide, or a silane-modified resin is used. And the silane crosslinking method.

  If the degree of crosslinking of the polyolefin-based resin is too high, the foaming ratio is lowered and the thermoformability is lowered. If it is too low, the thermal stability is lowered, and the cell during foaming (cell wall) ) May break, and uniform bubbles may not be obtained. Therefore, the gel fraction serving as an index for crosslinking is preferably 10 to 30% by weight, more preferably 15 to 25% by weight.

  In the present invention, the gel fraction means the percentage (weight) of the weight of the polyolefin resin foam before immersion in xylene after the polyolefin resin foam is immersed in xylene at 120 ° C. for 24 hours. It is.

  The pyrolytic foaming agent is not particularly limited as long as it has a decomposition temperature equal to or higher than the melting temperature of the expandable polyolefin resin sheet. For example, sodium bicarbonate, ammonium carbonate, an azide compound, Inorganic thermal decomposable foaming agents such as sodium borohydride, azodicarbonamide, azobisisobutyronitrile, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxybisbenzenesulfonylhydrazide, azodicarboxylic acid Organic pyrolytic foaming agents such as barium, trihydrazinotriazine, p-toluenesulfonyl semicarbazide and the like can be mentioned. Among them, azodicarbonamide, which is easy to adjust the decomposition peak temperature and decomposition rate, has a large amount of gas generation, and is excellent in hygiene, is preferably used.

  The amount of the pyrolytic foaming agent added is determined according to the foaming ratio according to the intended use of the laminated composite to be obtained, but if it is too small, a sufficient foaming ratio cannot be obtained, and if it is too large, there are many foam breaks. Therefore, the amount is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the polyolefin resin.

As a means for crosslinking the polyolefin-based resin, for example, in the case of an electron beam crosslinking method, a crosslinking aid such as divinylbenzene may be used.
The electron beam dose is preferably 1 to 20 Mrad, more preferably 3 to 10 Mrad.

In the silane crosslinking method, a crosslinking catalyst such as dibutyltin dilaurate or barium octoate may be used in addition to the silane-modified resin.
The addition amount of the crosslinking catalyst is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 0.1 parts by weight, with respect to 100 parts by weight of the polyolefin resin.

The crosslinking agent used in the chemical crosslinking method is not particularly limited, and examples thereof include dibutyl peroxide, dicumyl peroxide, tertiary butyl cumyl peroxide, diisopropyl peroxide and the like. Of these, tertiary butyl cumyl peroxide and dicumyl peroxide are preferably used.
The addition amount of the cross-linking agent is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight with respect to 100 parts by weight of the polyolefin resin.

  Means for preparing a foamable polyolefin resin sheet from the foamable polyolefin resin composition to which the above pyrolyzable foaming agent has been added are: a foamable polyolefin resin composition at a temperature lower than the decomposition temperature of the above pyrolyzable foaming agent. What is necessary is just to thermoform to the sheet | seat form of desired thickness, As the thermoforming means, the extrusion method using a T die or an inflation die, a press molding method, a calendering method, a blow molding method etc. are mentioned, for example. Among these, the extrusion molding method is preferably used from the viewpoint of productivity.

  In the present invention, the polyolefin resin foam that is the main member of the resin foam with a face material is such that individual bubbles are oriented in the thickness direction, and the bubbles constituting the foam as described above are: It has a spindle shape with its major axis oriented in the thickness direction, as if it were arranged like rugby balls upright in the same direction and aligned horizontally, and laminated in layers in the thickness direction. On the other hand, it shows a high elastic modulus.

  As described above, when the horizontally aligned cell layers are multi-layered in the thickness direction, the density of the central portion in the thickness direction of the polyolefin resin foam is smaller than the density of the surface portion. It is preferable that

As described above, the face material used in the present invention can suppress the foaming force in the in-plane direction when the foamable polyolefin resin sheet is heated and foamed, and the corners of the opening are less likely to be curved. It is limited to a nonwoven fabric made of polyethylene terephthalate resin in that a good groove shape can be easily obtained .

  The thickness of the face material is not particularly limited, but the viewpoint that the laminated composite of the present invention can be continuously produced in a long length by being compactly accommodated by means such as winding. To preferably a metal plate or the like, it is 1 mm or less, more preferably 0.3 mm or less. The above face materials other than the flexible metal plate may exceed the above thickness.

  The means for laminating the face material on the expandable polyolefin resin sheet is not particularly limited, and for example, a known laminator or the like is used.

  The heating and foaming means is not particularly limited. For example, a heating device such as hot air or a direct heating device such as an infrared heater is used to provide a take-up device on the outlet side. Foaming method while transporting, foaming method using an endless belt transporting device instead of the take-up device, continuous foaming method such as those in which the tunnel type heating furnace is vertical or horizontal, hot air thermostat For example, a foaming method using an oil bath, a metal bath, a salt bath, or the like may be used instead of a batch type foaming method such as the above, or a heat medium such as the hot air or a heat source.

As described above, the resin foam with a face material obtained in this way is aligned horizontally in a spindle shape in which the long axis is oriented in the thickness direction, and the bubbles constituting the polyolefin resin foam are further aligned. It becomes the structure laminated | stacked in layer form in the thickness direction.
Therefore, the cell formed by the amount restrained in the in-plane direction has a shape having a major axis in the thickness direction, thereby increasing the compression elastic modulus. In addition, since the face materials are laminated, the elastic modulus of the resin foam with face materials is increased by the reinforcing effect of the face materials themselves.
The major axis orientation fraction in the thickness direction of the foamed cell is preferably 60% or more, more preferably 80% or more.

The degree of orientation of the long axis in the thickness direction of the foamed cell, that is, the ratio of the long axis to the short axis can be controlled by the expansion ratio and the melt viscosity of the expandable polyolefin resin composition.
That is, since the expansion in the in-plane direction is suppressed by increasing the expansion ratio, the expansion in the thickness direction is increased, and the ratio of the major axis to the minor axis of the obtained foam cell is increased.

  When the melt viscosity is less than 8000 poise, the melt viscosity of the foamable polyolefin resin composition is too low, and the resin film of the cell is ruptured at the time of foaming, so that the spindle-shaped cells are not beautifully aligned and has a good elastic modulus. If the melt viscosity exceeds 25,000 poise, foaming is suppressed, the ratio of the major axis to the minor axis of the resulting foamed cell is small, and the desired compression modulus and bending rigidity are obtained. Therefore, preferable foaming conditions include, for example, blending of a foaming agent with a foaming ratio of 5 times or more in the range of melt viscosity of 8000 to 25000 poises of the foamable polyolefin resin composition.

  If the expansion ratio of the polyolefin resin foam is too low, a sufficient ratio of the major axis to the minor axis of the foam cell cannot be obtained as described above, and the desired elastic modulus cannot be obtained, and the lightweight property is also reduced. Loss and high cost, and if the ratio exceeds 20 times, the ratio of the major axis to the minor axis of the foam cell becomes large enough, but the individual cell walls become thin, and sufficient compression modulus is obtained. Preferably, the expansion ratio is 3 to 20 times because it cannot be expressed.

The average value of the aspect ratio Dz / Dxy of the internal bubbles is preferably 1.1 to 4.0.
The aspect ratio refers to the diameter of the foam cell in the z direction of the foam, that is, the thickness direction of the foam, Dz, and the diameter of the foam cell in the width and length direction of the foam, that is, the in-plane direction of the foam. When Dz / Dxy is less than 1.1, the desired compression modulus may be difficult to obtain, and Dz / Dxy exceeds 4.0. May cause excessive deformation of the polyolefin resin foam, which may make it difficult to manufacture.

  Further, if the compression elastic modulus is too small, buckling is likely to occur with a slight load, and therefore it is preferably 6 MPa or more.

The method for producing a thermoplastic resin foam having a concave groove according to the present invention has a cross-sectional shape in which the tip of the base portion 31 is formed as a bulging portion 32 as illustrated in FIGS. 1 and 2, for example. The mold 1 having the ridges 3 whose height h ₁ is equal to or greater than the maximum width d ₂ of the bulging portion 32 is heated so that the mold temperature is 180 to 220 ° C. , and is 1 to 2 seconds / cm. The groove is formed by pressing on the surface of the resin foam with a face material at a pressing speed, and then demolding after cooling.

  When pressing the mold 1 by pressing against the surface of the resin foam with face material at the above mold temperature and pressing speed, first, as shown in FIG. While being in contact with the face material 6, it is heated instantaneously and only the contact portion is softened. At the next moment, as shown in FIG. 5 (II), when the ridge 3 is pressed at a high speed, the softened portion of the face material 6 is preferentially deformed while the resin foam 7 is partially melted. When further pressed, as shown in FIG. 5 (III), the contact portion of the ridge 3 is preferentially deformed to form a groove along the ridge 3. Thereafter, the shape of the face material 6 and the resin foam 7 is maintained by cooling, and when the ridge 3 is pulled out as shown in FIG. 5 (IV), the groove 4 corresponding to the shape of the ridge 3 is formed. Further, it is possible to prevent the corners 9 and 9 of the concave groove 4 from being curved.

  In the above, if the mold temperature is too low, the face material 3 and the resin foam 7 are difficult to deform, and the opening corners 9 and 9 of the groove 4 are likely to be curved. Further, even when the mold temperature is too high, the face material 3 and the resin foam 7 become too soft, and the opening corners 9 and 9 are likely to be curved.

  On the other hand, if the pressing speed is too slow, the face material 3 and the resin foam 7 around the contact portion of the ridge 3 become too soft, the opening corners 9 and 9 are likely to have a curvature, and the pressing speed is too high. The face material 3 and the resin foam 7 are not easily deformed, and the opening corners 9 and 9 of the concave groove 4 are easily curved.

In the above, since it is non-woven fabric facing material 7 is made of polyethylene terephthalate resin, with less curvature in the opening corners 9, 9, good groove shape is not easy to obtain. In this case, the mold temperature is limited to 180 to 220 ° C.

In the present invention, the height h ₁ of the mold 1 of the ridges 3 has a smaller maximum width d ₂ of the cross section of the bulge portion 32, the concave groove which is formed when disposed pipes for floor heating Since the pipe does not fit or the pipe is easily removed from the concave groove, the maximum width d ₂ of the bulging portion 32 is set. The material of the mold 1 is preferably a metal or an alloy such as aluminum, copper, iron, zinc, and stainless steel.

  Moreover, it is preferable that the depth of the ditch | groove 4 is deeper than the outer diameter of the pipe laid. If it is shallower than the outer diameter of the pipe, a part of the pipe comes out on the surface of the resin foam 7 with the face material, and the effect of holding and protecting the pipe is reduced, and the part that comes out on the surface may be damaged.

  The width of the opening of the groove 4 needs to be narrower than the outer diameter of the pipe. If it is wider than the outer diameter of the pipe, the laid pipe cannot be held. To attach and detach the pipe, the opening of the resin foam with face material 7 can be deformed. The inner width of the groove 4 is preferably about the same as the outer diameter of the pipe, but if the pipe can be accommodated by deformation of the inner surface of the groove 4, there is no problem even if it is slightly narrower than the outer diameter of the pipe. .

According to the present invention, a polyolefin-based resin foam in which individual bubbles are oriented in the thickness direction is used, the base has a cross-sectional shape that is a bulging portion, and the height is the bulging portion. The mold provided with ridges that are equal to or larger than the maximum width of the mold is heated so that the mold temperature is 180 to 220 ° C. , and is applied to the surface of the resin foam with a face material at a pressing speed of 1 to 2 seconds / cm. Since the groove is formed by pressing, it is demolded after cooling, so it has good compressive strength, it is difficult to have a curvature at the opening corner of the groove , and a good groove shape is obtained. It is easy to be molded, and a pipe or a linear heater can be reliably held, and a thermoplastic resin foam having a concave groove with little environmental load can be provided.

  When the expansion ratio of the polyolefin resin foam is 3 to 20 times, the average value of the aspect ratio Dz / Dxy of the internal bubbles is 1.1 to 4.0, and the compression modulus is 6 MPa or more The compression strength of the obtained resin foam is improved, and the above effect is further ensured.

The present invention will be specifically described below by showing examples and comparative examples.
In addition, this invention is not limited only to the following Example.
(Creation of foam)
As a resin foam with a face material, a foaming olefin resin (melting point: 155 ° C.) composite sheet in which polyethylene terephthalate resin nonwoven fabric (weight per unit: 15 g / m ² , thickness: 100 μm, melting point: 255 ° C.) is laminated on both sides is heated in a heating zone. The resulting foam was heated at 230 ° C. for 8 minutes with a continuous foaming machine to obtain a polyolefin resin composite foam sheet with a face material. The obtained polyolefin-based resin composite foam sheet with a face material has a thickness of 10 mm, the expansion ratio of the polyolefin-based resin composite foam is 10 times, the average aspect ratio Dz / Dxy of the internal bubbles is 2, and the compression modulus is It was 23 MPa. The measurement method is shown below.
(aspect ratio)
The polyolefin resin foam was cut in the thickness direction (z direction), and an enlarged photograph of 15 times was taken while observing the center of the cross section with an optical microscope. Next, after measuring Dz and Dxy of all the bubbles shown in the photograph with a caliper, Dz / Dxy for each bubble is calculated, the number average of Dz / Dxy for 100 bubbles is calculated, and the aspect ratio Dz / The average value of Dxy was used. However, bubbles having an actual Dz of 0.05 mm or less and 10 mm or more were excluded.
(Foaming ratio)
The expansion ratio of the polyolefin resin foam was measured according to JIS K6767.
(Foam compression modulus)
Based on JIS K7220, the compression elastic modulus of the polyolefin resin foam was measured.

Example 1
1 and FIG. 2 has a cross-sectional shape, the tip of the base 31 is a bulge 32, the height h ₁ is 7 mm, the maximum width d ₂ of the bulge 32 is 5.6 mm, the base width The mold 1 made of aluminum provided with ridges 3 having a d ₁ of 4.5 mm (the pattern of the ridges 3 has a meandering shape as shown in FIG. 3) is set so that the mold temperature becomes 200 ° C. And is pressed against the surface of the resin foam with a face material at a pressing speed of 1.5 seconds / cm, then cooled and demolded to have a groove 4 as shown in FIGS. A resin foam 5 was obtained.

(Comparative Example 1)
A thermoplastic resin foam having a concave groove was obtained in the same manner as in Example 1 except that the mold temperature was 160 ° C.

(Comparative Example 2)
A thermoplastic resin foam having concave grooves was obtained in the same manner as in Example 1 except that the mold temperature was 250 ° C.

(Comparative Example 3)
A thermoplastic resin foam having a concave groove was obtained in the same manner as in Example 1 except that the pressing speed was 0.5 sec / cm.

(Comparative Example 4)
A thermoplastic resin foam having a concave groove was obtained in the same manner as in Example 1 except that the pressing speed was 3 seconds / cm.

The evaluation results for the above Examples and Comparative Examples are shown in Table 1. The groove shape and pipe holding force were evaluated by the following methods.
(Concave groove shape)
The width of the groove and the depth of the groove in the 1 mm portion and 4 mm portion from the top of the opening were measured. Moreover, the curvature of the opening corner was measured with an R gauge.
(Pipe holding power)
Cut out the thermoplastic resin foam so that the length of the groove is 10 cm, and fit a pipe (length: 15 cm) with an outer diameter of 6.0 mm into the groove so that both ends come out of the foam. After that, the pipes of the portions coming out from both ends were supported horizontally, a flat plate was fixed to the foamed body and pulled in the vertical direction with a tensile tester, and the force when the pipe was detached was measured.

  As is apparent from Table 1, in the examples of the present invention, it has been found that the curvature of the opening corner is small and an excellent pipe holding force is exhibited.

It is a schematic cross section which shows an example of the metal mold | die in this invention. It is an enlarged view which shows the protruding item | line 3 in FIG. It is a schematic plan view which shows an example of the thermoplastic resin foam which has a ditch | groove of this invention. It is sectional drawing of the thermoplastic resin foam which has a ditch | groove of FIG. It is a schematic cross section explaining an example of a method for producing a thermoplastic resin foam having a concave groove according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal mold | die 2 Board | substrate 3 Projection 31 Base 32 Expansion part 4 Concave groove 5 Thermoplastic resin foam which has a concave groove 6 Face material 7 Resin foam 9 Opening corner

Claims (2)

On both sides of a polyolefin resin foam in which individual bubbles are oriented in the thickness direction, a face material is formed of a polyethylene terephthalate resin nonwoven fabric to suppress the foaming force in the in-plane direction that occurs when foaming by heating. A method for producing a thermoplastic resin foam having a groove on at least one side of a resin foam with a face material, wherein the base has a cross-sectional shape in which the tip of the base is a bulge, and the height thereof is A mold provided with ridges that are equal to or larger than the maximum width of the bulging portion is heated so that the mold temperature is 180 to 220 ° C., and the resin foam with a face material is applied at a pressing speed of 1 to 2 seconds / cm. A method for producing a thermoplastic resin foam having a concave groove, wherein the concave groove is formed by pressing on a surface and then demolded after cooling. The expansion ratio of the polyolefin resin foam is 3 to 20 times, the average value of the aspect ratio Dz / Dxy of the internal bubbles is 1.1 to 4.0, and the compression modulus is 6 MPa or more. method for producing a thermoplastic resin foam having a concave groove of claim 1 Symbol mounting and.

Images