JP2006274038A - Uncrosslinked polyethylene-based resin extrusion-foamed body and molded body thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an uncrosslinked polyethylene-based resin extrusion-foamed body which is thermoformable in a wide range of temperatures and is excellent in the deep-drawing ability and to provide a molded body thereof. <P>SOLUTION: The uncrosslinked polyethylene-based resin extrusion-foamed body which is formed by extrusion-foaming a melt-foamable resin composition containing a polyethylene-based resin composition included with a foaming agent, is characterized in that the polyethylene-based resin composition composing the above foamed body has a tensile elongation when heated at 120°C and for 60 seconds of 240-350% and an MFR of 0.5-2.5 g/10 min, and in that the above foamed body has an apparent density of 15-460 g/L, a thickness of 1-10 mm, an open-cell ratio of 30% or less, and has such a DSC curved line obtained by the differential scanning calorimetric measurement as has at least two fusion calorific value peaks. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an uncrosslinked polyethylene resin extruded foam and a molded product thereof.

  Polyethylene resin foams are widely used in various applications such as buffer materials, heat insulating materials, and packaging materials. As the polyethylene resin foam, a crosslinked polyethylene resin foam that is crosslinked by electron beam irradiation or the like and then foamed using a chemical foaming agent, and non-crosslinked obtained by an extrusion method using a physical foaming agent without crosslinking. Polyethylene foam is available on the market. Cross-linked polyethylene foams have excellent properties such as heat resistance and thermoformability, and are therefore widely used in fruit vegetable containers, vehicle interior materials, industrial heat insulating materials, sports equipment, and the like. However, since an extra step is required for crosslinking, the cost is high, and the crosslinked foam cannot be recovered and reused by returning it to the original resin, so it is not suitable for the future recycling society. there were. On the other hand, in the non-crosslinked polyethylene resin foam by the extrusion method, a high-pressure method low-density polyethylene excellent in foamability has been put into practical use, but among polyethylene, branched low-density polyethylene is rigid, It has the disadvantage of being inferior in heat resistance and can only be used for soft packaging applications. Moreover, when the non-crosslinked polyethylene resin foam made of branched low-density polyethylene is thermoformed, the range of thermoforming due to a sudden change in viscosity was very narrow. In order to solve such problems, it has been proposed to use different polyethylenes in mixture (Patent Document 1, Patent Document 2).

  As a result of research to solve the above problems, the present inventors previously determined that the heat quantity of the endothermic curve peak of the non-crosslinked polyethylene resin foam (hereinafter also simply referred to as “endothermic peak”) and the cell structure are specific relational expressions. It has been found that the above problem can be solved by providing a non-crosslinked polyethylene resin foam for molding that satisfies the above (Japanese Patent Application No. 2003-374323).

JP-A-6-184346 JP 60-222222 A

  The above-mentioned non-crosslinked polyethylene resin extruded foam for molding previously proposed by the present applicant has excellent physical properties such as excellent surface smoothness and high rigidity, while using a general-purpose polyethylene resin, and thermoforming. It was excellent in nature. Further, since this foam does not need to be crosslinked, it has effects such as excellent cost and production efficiency and excellent recyclability. However, there is room for improvement in the moldable temperature range and deep drawability when thermoforming a deep drawn container.

  An object of the present invention is to solve the above-described problems, and to provide a non-crosslinked polyethylene resin extruded foam having a wide temperature range in which thermoforming is possible and good deep drawability, and a molded body thereof.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have made the above-mentioned problems by setting the tensile elongation and MFR at 120 ° C. for 60 seconds of the polyethylene resin composition constituting the foam to specific values. As a result, the present invention has been completed.

That is, the present invention
(1) A non-crosslinked polyethylene resin extruded foam obtained by extrusion foaming a melt foamable resin composition containing a foaming agent in a polyethylene resin composition, the polyethylene resin composition constituting the foam The tensile elongation during heating at 120 ° C. for 60 seconds is 240 to 350%, the MFR is 0.5 to 2.5 g / 10 minutes, the apparent density of the foam is 15 to 460 g / L, and the thickness is 1 to 10 mm, open cell ratio is 30% or less, non-crosslinked polyethylene resin extruded foam, characterized in that there are at least two melting calorie peaks on the DSC curve obtained by differential scanning calorimetry of the foam,
(2) The non-crosslinked polyethylene resin extruded foam according to (1) above, which contains a heat elongation modifier comprising a fatty acid compound,
(3) The non-crosslinked product according to (2), wherein the fatty acid compound is a mixture of a fatty acid compound A composed of a polyhydric alcohol and a partial ester of a fatty acid and a fatty acid compound B other than the fatty acid compound A Polyethylene resin foam,
(4) The non-crosslinked polyethylene resin extruded foam according to (3) above, wherein the fatty acid compound B is a fatty acid amide compound having 12 to 24 carbon atoms,
(5) A molded body obtained by thermoforming the non-crosslinked polyethylene resin extruded foam according to any one of (1) to (4) above,
Is a summary.

  The non-crosslinked polyethylene resin extruded foam of the present invention has excellent surface smoothness and good appearance while using a general-purpose polyethylene resin. In addition, since the foam of the present invention has a wide temperature range in which thermoforming is possible, even when heating temperature unevenness occurs when used in thermoforming, a uniform molded body can be thermoformed. Furthermore, the present invention has a good deep drawability, can prevent the formation of tears during thermoforming and can thermoform a good deep draw.

  In addition, if the non-crosslinked polyethylene resin extruded foam of the present invention is thermoformed, it is thermoformed using the foam of the present invention having excellent thermoformability as described above. It is possible to provide a good molded article having no irregularities, good appearance, no tearing, uneven thickness, and no surface burn. Even if it is a molded object shape | molded especially by deep drawing, if it is this invention, the favorable deep drawing molded object which does not generate | occur | produce a tear can be provided.

  And since the polyethylene resin used in the foam or molded product of the present invention is non-cross-linked, it is excellent in cost, production efficiency, recyclability, and adapted to the present when waste treatment (environmental problem) is strictly required. Is.

  In the non-crosslinked polyethylene resin extruded foam of the present invention, the polyethylene resin composition constituting the foam has a tensile elongation of 240 to 350% when heated at 120 ° C. for 60 seconds. When the tensile elongation at the time of heating of the resin composition is less than 240%, the foam does not stretch well when it is thermoformed using the foam molded from the resin composition, and it is cracked and uneven in thickness. Etc. are likely to occur, and the thermoformability may be deteriorated. On the other hand, if the tensile elongation at the time of heating of the resin composition exceeds 350%, the drawdown becomes large when thermoforming using a foam composed of the resin composition, so that the entire foam is made uniform. It becomes difficult to heat, and there is a possibility that the thermoformability is deteriorated. From the above viewpoint, the tensile elongation during heating described above is more preferably 245 to 320%, and further preferably 250 to 300%.

The tensile elongation of the polyethylene resin composition when heated at 120 ° C. conforms to JIS K7127 (1989). For example, Tensilon Universal Testing Machine manufactured by Orientec Co., Ltd. and constant temperature for tensile testing machine manufactured by Toyo Baldwin Co., Ltd. It can be measured by a combination of tanks. Specifically, using a No. 2 type test piece with a thickness of 1 mm, after being held for 60 seconds in a thermostat kept at 120 ° C., the measurement is performed under the conditions of a distance between grips of 80 mm and a test speed of 500 mm / min. Take the value. The measurement is performed five times or more, and the maximum value and the minimum value are removed from the measurement value, and the average value of the remaining values is adopted.
In addition, the test piece was defoamed with a heating press and a cooling press to obtain a non-foamed resin sheet, and the resin sheet and the resin sheet were laminated with a heating press and a cooling press so that the resin sheet had the thickness described above. We will use things. The reason why the tensile elongation at heating of 120 ° C. and 60 seconds is used is that it has been found that there is a correlation with the state of expansion of the foam during heating in actual thermoforming.

FIG. 1 shows a DSC curve obtained by heat flux differential scanning calorimetry of an uncrosslinked polyethylene resin extruded foam of the present invention. This DSC curve is obtained by heating about 3 mg of a sample cut from a foam to 200 ° C. at a heating rate of 10 ° C./min with a heat flux differential scanning calorimeter in accordance with JIS K7122 (1987), and cooling rate from 200 ° C. It can be obtained by a DSC curve obtained by performing a heat treatment at 10 ° C./min to 30 ° C. and then heating again to 200 ° C. at a heating rate of 10 ° C./min. The reason for adopting the DSC curve obtained by the second temperature increase is that a raw material composition advantageous in formability can be found without being affected by the thermal history.
The foam of the present invention has an endothermic curve peak heat amount in the temperature range of 40 to 112 ° C. in the DSC curve: A (J / g) and an endothermic curve peak heat amount in the temperature range of 112 ° C. or higher: B (J / The relationship shown by the following formula (1) is established between the above and g).
2.5 ≦ A / B ≦ 7 (1)
In addition, in this specification, the calorific value of the endothermic peak in the temperature range of 40-112 degreeC in the DSC curve of heat flux differential scanning calorimetry: A (J / g), and the endothermic curve peak in the temperature range of 112 degreeC or more As shown in FIG. 1, the heat quantity of B: (J / g) is defined as a point d where the endothermic curve peak is separated from the low temperature side baseline of the endothermic curve peak of the DSC curve, and the endothermic peak is the base on the high temperature side. A point returning to the line is a point e, a straight line m connecting the point d and the point e, and a value obtained from the area of the portion in the temperature range of 40 to 112 ° C. surrounded by the DSC curve is A (J / G), and B (J / g) is a value obtained from the area of the portion surrounded by the straight line connecting point d and point e and the DSC curve and having a temperature range of 112 ° C. or higher. . Also, the apparatus should be adjusted so that the baseline is as straight as possible. If the baseline is inevitably curved, for example, the curved baseline on the low temperature side of the endothermic peak is shown in FIG. An extension line x is drawn to the high temperature side so as to maintain the curved state, and the point where the endothermic peak departs from the low temperature side baseline including the drawn extension line x is point d, and the curved base line on the high temperature side of the endothermic peak An extension line y is drawn to the low temperature side so that the curved state of the curve is maintained, and a point where the endothermic peak returns to the high temperature side base line including the drawn extension line y is defined as a point e.

  As shown in FIG. 1, the heat amounts A and B correspond to the areas of hatched portions. Ratio of heat quantity of the endothermic peak in the DSC curve of the foam: When A / B is less than 2.5, the apparent density, thickness, open cell ratio, average cell diameter, cell shape, etc. of the foam are specified below. It may be difficult to obtain a foam having inferior rigidity such as appearance and compressive strength. Examples of the DSC curve when A / B is less than 2.5 include the DSC curve shown in FIG. In the case of a foam having A / B exceeding 7, the rigidity such as compressive strength is lowered, and there is a possibility that the temperature range that can be molded when the foam is thermoformed becomes narrow. From the above viewpoint, a more preferable range of A / B is 2.5 to 6, and a more preferable range is 2.5 to 5.

  In order to improve the rigidity of the foam, such as thermoformability and compressive strength, the calorific value of the endothermic curve peak in the temperature range of 112 ° C. or higher in the DSC curve: B (J / g) is 10 to 35 J / g. g is preferable, and 15 to 30 J / g is more preferable. When the amount of heat: B (J / g) is less than 10 J / g, moldability may be deteriorated, for example, the foam may be easily broken during thermoforming. On the other hand, when it exceeds 35 J / g, the open cell ratio is increased and the rigidity such as compressive strength may be lowered.

The polyethylene-based resin composition constituting the foam of the present invention has two or more, one or more at less than 112 ° C. and one or more at 112 ° C. or more of the DSC curve obtained by differential scanning calorimetry of heat flux. The endothermic peak is preferably from the viewpoints of widening the temperature range in which the foam can be molded when thermoforming and improving the heat resistance of the molded article formed by thermoforming.
Specifically, when there are two or more endothermic curve peaks as shown in FIG. 1, the difference between the temperature at the vertex S of the endothermic curve peak and the temperature at the vertex T of the endothermic curve peak is preferably 6 to 18 ° C. 8-15 degreeC is more preferable. If it does in this way, the temperature range which can be shape | molded at the time of thermoforming a foam is wide, and the moldability of a foam can be made still more favorable. FIG. 3 shows an example in which the difference between the temperature at the apex S of the endothermic curve peak and the temperature at the apex T of the endothermic curve peak exceeds 18 ° C. As described above, the foam in which the difference between the temperature of the vertex S and the temperature of the vertex T exceeds 18 ° C. may be broken when there is a portion that does not soften when thermoformed. When two or more endothermic curve peaks appear, the vertex of the endothermic curve peak having a large area below 112 ° C. is defined as S, and the vertex of the endothermic curve peak having a large area above 112 ° C. is defined as T.

  The foam having the endothermic curve peak with the A / B value of 2.5 to 7 described above was dispersed in a polyethylene resin without uneven distribution of polyolefin components such as ultra-high molecular weight polypropylene and polyethylene by a catalyst technique. It can be obtained using a single component polyethylene resin or using a two component polyethylene resin in which two or more polyethylene resins are mixed. Among these, a two-component polyethylene resin that can easily obtain a desired endothermic curve peak will be described below. Examples of the two-component polyethylene resin include a combination of two or more polyethylene resins having different melting points. As a difference of melting | fusing point of both resin, 6-18 degreeC is preferable and 8-15 degreeC is more preferable.

In this specification, the value measured with the following method is employ | adopted for melting | fusing point of a polyethylene-type resin and a polyethylene-type resin composition.
Measured by a method according to JIS K7121 (1987), 2-4 mg of a raw material pellet sample was taken, and the temperature was increased from 23 ° C. to 200 ° C. at a heating rate of 10 ° C./min using a thermal flow rate differential scanning calorimeter. The temperature at the top of the endothermic curve peak is calculated from the DSC curve obtained by lowering the temperature to 40 ° C. at a cooling rate of 10 ° C./min and then increasing the temperature at a heating rate of 10 ° C./min. And When two or more endothermic curve peaks appear, the temperature at the apex of the endothermic curve peak having the largest area is defined as the melting point. However, when there are a plurality of endothermic curve peaks with the largest area, the temperature at the apex of the endothermic curve peak on the highest temperature side among the endothermic curve peaks is taken as the melting point.

  The amount of heat at the endothermic curve peak: B (J / g) preferably corresponds to the amount of heat at the endothermic curve peak within a temperature range of 112 ° C. or higher and 130 ° C. or lower. If the ratio of the amount of heat at the endothermic peak on the high temperature side of 130 ° C. or higher is large in the value of the amount of heat B, there is a risk that the expansion ratio will decrease and the open cell ratio will increase. Further, the endothermic peak of less than 112 ° C. in the DSC curve usually exists in the temperature range of 40 ° C. to 112 ° C., but there is also an endothermic peak below 40 ° C., and the endothermic curve peak of less than 40 ° C. Even when the ratio is large, the expansion ratio is lowered and the open cell ratio is increased. Therefore, the endothermic curve peak is in the temperature range of 40 ° C to 112 ° C. When the heat quantity of the endothermic curve peak in the temperature range of 112 ° C. or higher and 130 ° C. or lower is B ′ (J / g), B ′ (J / g) is preferably 10 to 35 J / g, and 15 to 30 J / g. Is more preferable. Moreover, the preferable range of A / B 'is 2.5-7, and a more preferable range is 2.5-5.

In order to make the foam satisfying the relationship represented by the above (1), the heat quantity of the endothermic peak: A (J / g) and the heat quantity: B (J / g), the polyethylene resin composition constituting the foam is It is preferable that it is a mixture of the following main polyethylene and subpolyethylene. Specifically, the main polyethylene is a branched low-density polyethylene, and the secondary polyethylene is one or a mixture of two or more selected from linear low-density polyethylene, high-density polyethylene, and linear ultra-low-density polyethylene. More preferably, the secondary polyethylene includes linear low density polyethylene, and it is particularly preferable to use only linear low density polyethylene. In particular, if the foam is made of a resin composition containing branched low-density polyethylene as the main polyethylene and linear low-density polyethylene as the sub-polyethylene, the foam breaks when thermoformed using the foam. It is difficult and is preferable because the temperature range in which thermoforming can be performed becomes wide. In this case, there are two endothermic curve peaks when the heat of fusion peak is less than 112 ° C. and one endothermic curve peak at 112 ° C. or higher. The branched low density polyethylene referred to in the present specification is a branched low density polyethylene obtained by a high-pressure method, and has 10 to 30 short chain branches per 1000 carbons as a short chain distribution. It has long chain branching. The long chain branch is preferably a long chain branch having a chain length corresponding to the main chain. The linear low density polyethylene referred to in this specification is a linear low density polyethylene made of a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms obtained by a medium-high pressure method. Usually, the short chain distribution has 3 to 25 short chain branches per 1000 carbons, but no long chain branches. The short chain branch is a chain length of 1 to 6 carbons, and the long chain branch is a chain length of at least 20 carbons. Usually, linear low density polyethylene contains 99.9 to 90 mol% of structural units obtained from ethylene and 0.1 to 10 mol% of structural units obtained from an α-olefin having 3 to 10 carbon atoms.
It is preferable to use, as a base resin, a resin in which these are blended in a weight ratio of main polyethylene: subpolyethylene = 60: 40 to 85:15.
In addition, in order to make it the preferable range 2.5-7 of A / B ', using the resin mix | blended by the ratio of main polyethylene: subpolyethylene = 60: 40-85: 15 by weight ratio is used as base resin. preferable.
Further, when the secondary polyethylene contains linear low-density polyethylene, the proportion of the linear low-density polyethylene in the secondary polyethylene is preferably 50% by weight or more from the viewpoint that the foam is difficult to break when thermoforming. 60% by weight or more is more preferable. In particular, it is preferably 70% by weight or more.

The branched low density polyethylene as the main polyethylene is produced by a high pressure method.
Moreover, the linear low density polyethylene, the high density polyethylene, and the ultra low density polyethylene as the secondary polyethylene are produced by a medium-low pressure method.

  The branched low density polyethylene used for the main polyethylene preferably has a density exceeding 910 g / L and not more than 930 g / L.

  On the other hand, the linear low density polyethylene used for the secondary polyethylene is preferably one having a density of 915 g / L to 940 g / L and a melting point of 120 to 130 ° C. The high density polyethylene preferably has a density exceeding 930 g / L and not more than 970 g / L, and the ultra-low density polyethylene preferably has a density of not less than 885 g / L and not more than 910 g / L.

  The non-crosslinked polyethylene resin foam of the present invention has a tensile elongation of 240 to 350% when heated at 120 ° C. for 60 seconds of the polyethylene resin composition constituting the foam as described above, and the resin composition The melt flow rate (hereinafter referred to as MFR) is 0.5 to 2.5 g / 10 min. When the tensile elongation and MFR at the time of heating of the resin composition are within the above-described ranges, the foam obtained by using this has excellent surface smoothness and good appearance, and a wide temperature range in which thermoforming can be performed. Therefore, the deep drawability is particularly good, and it is possible to prevent the molded body from tearing during thermoforming. In the present invention, the term “MFR” refers to the MFR of the composition when the polyethylene resin composition is composed only of the main polyethylene, and the polyethylene resin composition is composed of the main polyethylene and the sub polyethylene. Is the MFR of the composition.

  When the MFR of the polyethylene-based resin composition is less than 0.5 g / 10 minutes, the appearance of the foam molded using the same is likely to be deteriorated and the open-cell formation tends to occur and the thermoformability may be deteriorated. . From the above viewpoint, it is more preferably 0.55 g / 10 minutes or more, further preferably 0.6 g / 10 minutes, and particularly preferably 0.65 g / 10 minutes. On the other hand, when the MFR of the polyethylene-based resin composition exceeds 2.5 g / 10 minutes, the heat resistance of the foamed sheet is lowered, and the drawdown is increased during the thermoforming, so that the thermoformability is deteriorated. There is a fear. From the above viewpoint, it is more preferably 2.0 g / 10 min or less, further preferably 1.5 g / 10 min or less, and particularly preferably 1.0 g / 10 min or less.

  In addition, 0.1-3 g / 10min is preferable and, as for MFR of the main polyethylene which comprises the polyethylene-type resin composition used for this invention, 0.2-2 g / 10min is more preferable. When the MFR of the main polyethylene is less than 0.1 g / 10 min, the foam molded using the main polyethylene is likely to be open-celled and the rigidity such as compressive strength may be reduced. Moreover, when MFR of main polyethylene exceeds 3 g / 10min, there exists a possibility that a foam with a low apparent density of the foam shape | molded using this may not be obtained.

  On the other hand, when the polyethylene-based resin composition used in the present invention is composed of main polyethylene and sub-polyethylene, the MFR of the sub-polyethylene is preferably 3 to 30 g / 10 min, and preferably 4 to 20 g / 10 min. More preferable are those of 4 to 10 g / 10 min. When the MFR of the secondary polyethylene is less than 3 g / 10 minutes, the foam molded using the resin resin composition containing the secondary polyethylene may be deteriorated in appearance and in rigidity such as compression strength due to open cell formation. In addition, when it exceeds 30 g / 10 minutes, the heat resistance of the foam is lowered, the drawdown is increased during thermoforming, and the moldability is deteriorated.

  The MFR is a value measured at 190 ° C. and a load of 21.17 N according to JIS K7210 (1976).

  The non-crosslinked polyethylene resin extruded foam of the present invention is a foam having an apparent density of 15 to 460 g / L.

When the apparent density of the foam is less than 15 g / L, the above-mentioned endothermic curve peak heat ratio: A / B, rigidity such as compressive strength, even if the average cell diameter and cell shape described below satisfy the preferred ranges May become insufficient. From the said viewpoint, 18 g / L or more is more preferable, and 23 g / L or more is further more preferable. On the other hand, when it exceeds 460 g / L, the buffering property, the heat insulating property and the like become insufficient. From the above viewpoint, the density of the foam is more preferably 300 g / L or less, further preferably 230 g / L or less, and particularly preferably 150 g / L or less. In particular, 23 to 100 g / L is preferable from the viewpoint of improving buffering properties so that the surface of fruit and vegetables such as peach, tomato and pear is less likely to be damaged.
The apparent density of the foam was measured as follows.
By the method described later, the thickness of the foam is measured, and the basis weight of the foam is further measured.
The basis weight of the foam was calculated by cutting out a test piece having a length of 250 mm × width 250 mm × sheet-like foam, measuring the weight (g) of the test piece, multiplying the value by 16, and converting it to a weight per 1 m ^2. The value obtained (g / m ² ) is adopted.
The apparent density of the foam was determined by converting the basis weight (g / m ² ) of the foam obtained as described above by the thickness (mm) of the foam, in units (g / L). Adopt value.

  The foam of the present invention has a thickness of 1 to 10 mm. When the thickness of the foam is less than 1 mm, particularly when a molded body such as a container is molded, the thickness of the molded body becomes insufficient, the buffering property is lowered, and the shape retainability of the molded body becomes insufficient. This causes a problem such that the molded body loses its shape when stored. On the other hand, when the thickness exceeds 10 mm, the thickness of the foam is non-uniform and the appearance is deteriorated, and it becomes difficult to uniformly heat the inside of the foam during molding, so that the moldability is deteriorated. From the above viewpoint, the thickness of the foam is more preferably 1.5 to 8 mm, and further preferably 1.5 to 6 mm.

In addition, although the thickness of the foam as used in this specification may have a polyolefin-type resin layer on at least one side so that it may mention later, the said thickness says the thickness which does not contain a resin layer in that case. The thickness of the foam is measured as follows.
First, the foam is cut perpendicular to the direction perpendicular to the extrusion direction, the thickness of the cut surface is photographed at 10 points in the width direction at equal intervals by a microscope, and the thickness of the foam at each photographed point is measured, The arithmetic average value of the obtained values is taken as the thickness of the foam. In addition, when having a polyethylene-based resin layer on at least one side of the foam, at each point photographed as described above, the thickness of the foam and the thickness of the resin layer are respectively measured, and the arithmetic average value of the obtained measured values Are the thickness of the foam and the thickness of the resin layer. In addition, when it is difficult to distinguish between the foam and the resin layer, either the foam or the resin layer can be colored.

In the case where the resin layer is laminated on the foam and the resin layer cannot be easily peeled off, the apparent density of the foam is the basis weight (g / m ² ) of the foam, the thickness of the foam The value divided by (mm) is obtained by converting the unit to (g / L).
The basis weight of the foam (g / m ²⁾ of, after obtaining the basis weight of the whole including the resin layer (g / m ^2), subtracting the basis weight of the resin layer (g / m ²⁾ Ask for.
The basis weight (g / m ² ) of the resin layer is the thickness of the resin layer converted into m units to the density of the resin layer (for example, 0.9 × 10 ⁶ g / m ³ in the case of polypropylene). It is obtained by multiplying (m).

  Furthermore, the foam in the present invention has an open cell ratio of 30% or less. If the open cell ratio of the foam exceeds 30%, even if the heat quantity, average bubble diameter, bubble shape, etc. satisfy the above-mentioned requirements, the rigidity such as compressive strength is reduced, the buffering property is excellent, and the thickness is thin. There is a possibility that a molded body having rigidity may not be obtained, and a molded body having a shape as in a mold cannot be obtained when molded. From the above viewpoint, the open cell ratio of the foam is more preferably 28% or less, and further preferably 26% or less. Most preferably, it is 0%.

Foam open cell ratio: S (%) is a foam measured in accordance with Procedure C described in ASTM D2856-70 and using an air comparison type hydrometer 930 type manufactured by Toshiba Beckman Co., Ltd. The actual volume (the sum of the volume of closed cells and the volume of the resin portion): a value calculated from the following equation (2) from Vx (L).
S (%) = (Va−Vx) × 100 / (Va−W / ρ) (2)

However, Va, W, and ρ in the above equation (2) are as follows.
Va: Apparent volume (L) calculated from the outer dimensions of the foam specimen used for measurement
W: Weight of test piece (g)
ρ: Density of resin constituting the test piece (g / L)
The density ρ (g / L) of the resin constituting the test piece and the weight W (g) of the test piece are obtained by performing the operation of defoaming the foam test piece with a hot press and then cooling it. It can be obtained from the test piece. Even when there is a resin layer on at least one side to be described later, it can be measured in the same manner as described above.

In the present invention, it is preferable to add a heat elongation modifier comprising a fatty acid compound. The heat elongation modifier referred to in the present specification is added to the polyethylene resin composition constituting the foam of the present invention, so that when the foam composed of the resin composition is thermoformed, The thing which can improve the elongation of this heated foam. Specifically, as described above, it is preferable to add a heat elongation modifier so that the tensile elongation of the polyethylene resin composition when heated at 120 ° C. for 60 seconds is 240% or more. The upper limit of the tensile elongation at the time of heating is preferably 350% because there is a possibility that the drawdown at the time of thermoforming increases. A polyethylene resin composition having an MFR of 0.5 to 2.5 g / 10 min in addition to the tensile elongation during heating is preferred. Furthermore, the thing which can prevent the shrinkage | contraction at the time of extrusion is preferable.
A conventionally known fatty acid compound can be used as the heat elongation modifier comprising the fatty acid compound. More specifically, for example, fatty acid compounds such as fatty acid type, fatty acid amide type, and fatty acid ester type are used.

Specific examples of the fatty acid compound used as the heat elongation modifier include stearic acid, lauric acid, myristic acid, palmitic acid, arachidic acid, behenic acid, 12-hydroxystearic acid, and the like.
Specific examples of the fatty acid amide compound used as the heat elongation modifier include, for example, stearic acid amide, palmitic acid amide, oleic acid amide, erucic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, ethylene Examples thereof include bisoleic acid amide and ethylene bishydroxystearic acid amide.
Specific examples of the fatty acid ester-based compound used as the above-described heat elongation modifier include butyl stearate, stearic acid monoglyceride, oleic acid monoglyceride, behenic acid monoglyceride, ricinoleic acid monoglyceride, hydroxystearic acid triglyceride, sorbitan Fatty acid ester, polyoxyethylene (5) glycerol monostearate, polyoxyethylene (20) glycerol monostearate, polyoxyethylene (5) monooleate, pentaerythritol tetrastearate, polyadipic acid pentaerythrole stearate, stearyl stearate 1,2-oxystearic acid, hardened castor oil, and the like.
Usually, these fatty acid compounds are used in the form of a masterbatch and added to the foamable polyethylene resin composition in advance.

The viewpoint that the heating elongation modifier used in the present invention is a mixture of a fatty acid compound A composed of a polyhydric alcohol and a partial ester of a fatty acid and a fatty acid compound B other than the fatty acid compound A and has a smooth surface and excellent appearance. To preferred. Specific examples of the fatty acid compound A include monostearic acid glyceride, monopalmitic acid glyceride, monobehenic acid glyceride, monoolefinic acid glyceride, and monolauric acid glyceride. Among the above-mentioned, monostearic acid glyceride is preferable from the viewpoint that the open cell ratio can be lowered with a small amount, and thereby thermoforming is excellent. On the other hand, as the fatty acid compound B, the fatty acid compound, the fatty acid amide compound, and the fatty acid ester compound described above can be used, and particularly from the viewpoint of improving the tensile elongation during heating, the fatty acid amide compound is preferable. Among these, fatty acid amide compounds having 12 to 24 carbon atoms are preferable from the viewpoint of improving the tensile elongation during heating in a small amount.
In the present invention, the term “polyhydric alcohol” means an alcohol having two or more hydroxyl groups in the same molecule.

  The heating elongation modifier is preferably blended in an amount of 0.6 to 3.5 parts by weight with respect to 100 parts by weight of the polyethylene resin composition. If it is less than 0.6 parts by weight, there is a possibility that it does not contribute to the expansion of the foam during thermoforming. From the above viewpoint, 0.8 part by weight or more is more preferable, 1 part by weight or more is further preferable, and 1.2 part or more is particularly preferable. On the other hand, if the upper limit exceeds 3.5 parts by weight, the open cell ratio may be increased and the thermoformability may be deteriorated. From the above viewpoint, 3 parts by weight or less is more preferable, and 2.5 parts by weight or less is more preferable. In particular, in the heating elongation modifier composed of the fatty acid compound A and the fatty acid compound B described above, the fatty acid compound A is preferably blended in an amount of 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the polyethylene resin. It is more preferable to mix 7 to 1.3 parts by weight, and it is preferable to mix 0.1 to 2.0 parts by weight of the fatty acid compound B, more preferably 0.1 to 1.5 parts by weight, Thereby, both the shrinkage prevention at the time of heating of the foam to be molded and the tensile elongation at the time of heating are preferably improved, which is preferable. Furthermore, the weight ratio between the fatty acid compound A and the fatty acid compound B is preferably 50:50 to 85:15. When the fatty acid compound A is less than 50, there is a possibility that shrinkage of the foam tends to occur or surface smoothness may be lowered. Moreover, although the shrinkage | contraction of the foam obtained when the fatty-acid compound A exceeds 85, there exists a possibility that the elongation at the time of thermoforming may fall although it is suppressed.

  In the non-crosslinked polyethylene resin extruded foam of the present invention, the average cell diameter in the extrusion direction: X (mm) and the average cell size in the width direction: Y (mm) are 0.5 to 1.5 mm, respectively. When either one of the average cell diameter in the extrusion direction and the average cell diameter in the width direction is less than 0.5 mm, the corrugate and the foam with large thickness unevenness are obtained. In addition, the rigidity such as compressive strength also decreases. From the above viewpoint, 0.6 mm or more is more preferable, 0.8 mm or more is further preferable, and 0.9 mm or more is particularly preferable. On the other hand, when either one of the average cell diameter in the extrusion direction and the average cell size in the width direction exceeds 1.5 mm, the appearance of the foam and the appearance of the molded body obtained by thermoforming the foam are deteriorated. From the above viewpoint, the average cell diameter in the extrusion direction and the width direction is more preferably 1.4 mm or less, further preferably 1.35 mm or less, and particularly preferably 1.3 mm or less.

When the average cell diameter in the thickness direction is Z (mm), the following formulas (3) and (4) are preferably satisfied in the foam of the present invention.
0.6 ≦ Z / X ≦ 1.1 (3)
0.6 ≦ Z / Y ≦ 1.1 (4)
If the values of Z / X and Z / Y are in the ranges indicated by the above formulas (3) and (4), the foam has excellent compressive strength, and the foam has good extensibility during thermoforming. The closer the value of / X, Z / Y is to 1.0, that is, the closer the bubble shape is to a spherical shape, the better the compressive strength of the foam and the better the extensibility of the foam during thermoforming. When the values of Z / X and Z / Y are less than 0.6, the foamability is poor and the moldability such as cracking tends to deteriorate when thermoforming. From the above viewpoint, the range of Z / X and Z / Y is more preferably 0.7 or more, and further preferably 0.8 or more. On the other hand, when it exceeds 1.1, there is a thickness unevenness called corrugation and the appearance is poor, and when thermoforming, the moldability such as easy cracking from a thin portion is deteriorated. From the above viewpoint, the range of Z / X and Z / Y is more preferably 1.05 or less, and further preferably 1.0 or less.

  The average bubble diameter X in the extrusion direction, the average bubble diameter Y in the width direction, and the average bubble diameter Z in the thickness direction are respectively measured as follows.

Average cell diameter in the width direction: A line segment with a length of 30 mm is drawn in the width direction near the center of the vertical cross section perpendicular to the extrusion direction of the foam, and the number of bubbles on the line segment is measured. A value obtained by dividing the length of minutes by the number of bubbles is adopted as an average bubble diameter in the width direction: X (mm).
Average cell diameter in the extrusion direction: The center part in the width direction of the foam is cut perpendicularly along the extrusion direction, and a line segment having a length of 30 mm is drawn near the center part of the cross section in the extrusion direction. The number of bubbles is measured, and the value obtained by dividing the length of the line segment by the number of bubbles is adopted as the average bubble diameter in the extrusion direction: Y (mm).
Average cell diameter in the thickness direction: The width direction center part of the cut foam test piece was cut vertically along the extrusion direction, and a line segment was drawn near the center part in the cross section of the test piece. The number of bubbles on this line segment is measured, and the value obtained by dividing the length of the line segment by the number of bubbles is adopted as the average cell diameter in the thickness direction: Z (mm).
Note that the starting points of these line segments are drawn from the outer end of the bubble wall.

The term “non-crosslinked” as used herein refers to a case where the boiling xylene insoluble content is 5% by weight or less, and the proportion of the insoluble content is more preferably 3% by weight or less, and 0% by weight. Most preferred. The smaller the insoluble content, the easier it is to reuse. Boiling xylene insoluble matter is defined in JIS Z8801 (1996) after approximately 1 g of a precisely weighed foam test piece (the weight of the test piece is L (g)) is immersed in 100 g of boiling xylene for 8 hours. The solution is quickly filtered through a wire mesh having a mesh size of 74 μm, and the weight (M (g)) of the insoluble matter remaining on the wire mesh is measured.
Boiling xylene insoluble content: N (% by weight) = (M ÷ L) × 100 (5)
The boiling xylene insoluble content N of the resin composition constituting the foam of the present invention is also measured by the same method as described above.

  A polyolefin resin layer may be laminated on at least one surface of the foam of the present invention. If the foam has a polyolefin resin layer of 5 μm or more on at least one side, the functional additive can be added to the resin layer in a small amount without adding a large amount to the entire foam. Since an effect increases, it is preferable. The thickness of the resin layer provided on at least one side of the foam increases the rigidity, such as less drooping when holding the end of one side of the foam. When a certain container is thermoformed, the thickness is preferably 10 μm or more because the foam is difficult to break, and more preferably 15 μm or more from the viewpoint of further improving the rigidity. The thicker the resin layer, the higher the rigidity. However, if the thickness is too thick, the weight may increase and the lightness may be inferior. Therefore, the thickness of the resin layer is preferably 150 μm or less, more preferably 100 μm or less. . In particular, when a polyolefin resin layer is provided on both sides, the thickness of the resin layer on one side is preferably 80 μm or less. The polyolefin resin layer can be formed by a known method such as thermal lamination, extrusion lamination, coextrusion or the like in which a polyolefin resin film is laminated on a foam. The thickness of the resin layer is the same as the method for measuring the thickness of the foam described above.

  Examples of the olefin resin constituting the resin layer include polypropylene resin and polyethylene resin. Among these, a polyolefin-based resin that is easily heat-sealed with a foam is preferable because the resin layer can be laminated without using an adhesive layer. If the resin layer is a polyethylene resin, the whole can be recycled as a polyethylene resin. Examples of the polyethylene resin include ethylene homopolymers such as high density polyethylene, branched low density polyethylene, and linear low density polyethylene, ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, ethylene-propylene- Ethylene copolymers such as butene-1 copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-octene-1 copolymer A polymer, and also a mixture of two or more of these may be mentioned.

  The polyolefin resin constituting the polyolefin resin layer is a styrene resin such as polystyrene, an elastomer such as ionomer or ethylene propylene rubber, or a butene resin such as polybutene, as long as the purpose and effect of the foam of the present invention are not impaired. Can be added. In this case, the amount added is preferably 40% by weight or less, more preferably 25% by weight or less, and particularly preferably 10% by weight or less.

  Examples of the polyolefin resin constituting the polyolefin resin layer include functions such as a nucleating agent, an antioxidant, a heat stabilizer, an antistatic agent, a conductivity imparting agent, a weathering agent, an ultraviolet absorber, and a flame retardant. Various functional additives such as a functional additive and an inorganic filler may be added.

  In the foam of the present invention, when having a resin layer on at least one side, if the polyolefin resin constituting the resin layer contains an antistatic agent, the resin layer has antistatic properties, so that dust is caught. Therefore, it becomes a foam suitable for food and machine parts.

  The foam of the present invention is obtained by a T die, an annular die or the like attached to the tip of an extruder. Among these, an annular die is preferable from the viewpoint that a relatively 1000 mm width can be easily obtained.

Hereinafter, the manufacturing method of the foam at the time of using a cyclic | annular die is demonstrated.
The foam of the present invention has an endothermic curve peak heat amount in the temperature range of 40 ° C. to 112 ° C. in the DSC curve obtained by the differential scanning calorimetry of the foam described above: A (J / g), and 112 ° C. or more. It is preferable to use a polyethylene-based resin composition in which the heat quantity at the endothermic curve peak in the temperature range: B (J / g) satisfies the relationship of 2.5 ≦ A / B ≦ 7. Such a polyethylene resin composition may be a single component or two or more polyethylene resins in which a polyolefin component such as ultra-high molecular weight polypropylene or polyethylene is dispersed in the polyethylene resin by a catalyst technique without being unevenly distributed. The two-component thing which mixed was mentioned. Among these, a two-component one is preferable because the value of A / B can be easily within the above-described range. Hereinafter, the two components will be described.
For example, it is obtained by melting a mixture of main polyethylene and sub-polyethylene in an extruder and kneading with a foaming agent, and then extruding and foaming a foamable molten polyethylene resin composition from the inside of the extruder through a circular die to a low pressure region. Can do.

  Furthermore, it is preferable that a heat elongation modifier is added to the polyethylene resin composition. By adding the heat elongation modifier, shrinkage when the foam is extruded can be suppressed, and the resulting foam is improved in elongation during thermoforming. Furthermore, since the lower MFR can be used for the main polyethylene and the sub-polyethylene in the polyethylene-based resin composition by the heat elongation modifier, the selection of the resin is expanded. Moreover, since the melting temperature at the time of extrusion can be lowered, a foam having a low open cell ratio can be obtained, or the discharge amount can be increased.

By using a polyethylene resin composition that satisfies the above-mentioned A / B relationship, and further, by making the die shape into a shape that can suppress the heat generation of the foamable molten polyethylene resin composition, it is particularly open-celled. The foam of the present invention having a low rate can be obtained. The annular die has a shape that does not largely block the flow of the resin composition when the resin composition passes through the secondary breaker portion that supports the shaft, and the cross-sectional area of the resin composition flow path per discharge amount of the secondary breaker portion. It is important to control. For example, the following equation (6) is between the discharge amount per unit time in the secondary breaker part: P (kg / hr) and the cross-sectional area of the resin composition flow path in the secondary breaker part: Q (mm ² ). Design the die to hold.
30 ≦ Q / P ≦ 120 (6)

  When the Q / P is within such a range, heat generation when the resin composition passes through the secondary breaker can be sufficiently suppressed, and a pressure suitable for foaming can be maintained. As a result, the density, thickness, open cell ratio, average cell diameter, cell shape, etc. can be easily adjusted, resulting in a foam excellent in appearance, mechanical strength, thermoformability and the like. In addition, it is preferable from the viewpoint of suppressing heat generation that the cross-sectional area of the flow path of the secondary breaker is the same cross-sectional area on both the inlet side and the outlet side.

  While using a die having a shape capable of suppressing the heat generation of the resin composition as described above, the temperature of the die is accurately controlled by means such as oil temperature control, and the temperature of the foamable resin composition up to an appropriate extrusion foaming temperature upon extrusion. It is also important to lower It is particularly preferable to adjust the proper extrusion foaming temperature of the main polyethylene.

  The appropriate extrusion temperature is a temperature at which a foam within the range of the apparent density and open cell ratio in the present invention can be easily obtained. The specific temperature range is [crystallization temperature + 5 ° C.] or more and [crystallization temperature + 30 ° C.] or less of the main polyethylene, from the viewpoint of suppressing the improvement of the open cell ratio of the foam and the shrinkage of the obtained foam. To preferred. The measurement shall adopt the value measured with the thermometer in the position between the front-end | tip of an extruder, and die | dye.

  In this specification, the crystallization temperature of the main polyethylene is measured by a method according to JIS K7122 (1987). Details are as follows. 2-4 mg samples of raw material pellets are collected, and the temperature is raised from room temperature 23 ° C. to 200 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter, and then the temperature is lowered to 40 ° C. at a cooling rate of 10 ° C./min. And measure. Using the curve obtained when the temperature is lowered to 40 ° C. at a cooling rate of 10 ° C./min, the temperature at the peak apex is set as the crystallization temperature. When two or more exothermic curve peaks (hereinafter also simply referred to as “exothermic peaks”) appear, the temperature at the apex of the exothermic peak having the largest area is defined as the crystallization temperature. However, when there are a plurality of exothermic peaks having the largest area, the peak of the highest exothermic peak among them is defined as the crystallization temperature.

The method for adjusting the average cell diameter depends on the polyethylene-based resin used, for example, a method for reducing the average cell diameter by increasing the pressure of the die, a method for adjusting the amount of the cell regulator described later, and the like. It is done.
Moreover, although the value of Z / X and Z / Y depends on the polyethylene resin used, it can be adjusted by the discharge amount, the take-up speed, and the like. For example, when the bubbles are made flat in the extrusion direction, specifically, when the value of Z / X is 0.6 ≦ Z / X <1.0, the discharge amount is decreased, the take-up speed is increased, etc. It can be adjusted by the method. On the other hand, when the bubbles are almost spherical in the extrusion direction, specifically, when the value of Z / X is 1.0 ≦ Z / X ≦ 1.1, the discharge amount is increased, the take-off speed is decreased, etc. It can be adjusted by the method.
When forming flat bubbles in the width direction, specifically, when the value of Z / Y is 0.6 ≦ Z / Y <1.0, a method of extruding the foam so as to spread in the width direction In the case of using an annular die, the ratio of the outlet diameter of the annular die to the diameter of the mandrel as the cylindrical cooling device (the diameter of the mandrel as the cylindrical cooling device / the outlet diameter of the annular die) is increased. It can be adjusted by the method.
On the other hand, when the bubble shape in the width direction is a substantially circular bubble, specifically, when the value of Z / Y is 1.0 ≦ Z / Y ≦ 1.1, the foam is in the width direction. It can be adjusted by a method of extruding so as not to spread, and when an annular die is used, it can be adjusted by a method of lowering the ratio between the discharge port diameter of the annular die and the diameter of a mandrel that is a cylindrical cooling device. Further, it is possible to adjust by combining methods such as decreasing or increasing the discharge amount and decreasing or increasing the take-up speed.

In order to adjust the open cell ratio of the foam to 30% or less, the above-mentioned polyethylene resin composition in the range of A / B is used and, for example, the discharge amount per unit time in the secondary breaker part: P (kg / Hr) and the cross-sectional area of the resin composition flow path in the secondary breaker section: Q (mm ² ) so that the above-described formula (6) is satisfied, and the amount of the bubble regulator is described later. Or the foaming temperature of the main polyethylene [crystallization temperature + 5 ° C.] or more and [crystallization temperature + 30 ° C.] or less, the average cell diameter in the extrusion direction and the average cell diameter in the width direction However, in the resin composition having an MFR of 0.5 to 2.5 g / 10 min, the MFR of the main polyethylene is preferably 0.1. ~ 3g / 10min, more preferred Alternatively, it can be adjusted by adjusting the amount to 0.2 to 2 g / 10 minutes. The MFR of the secondary polyethylene is preferably 3 to 30 g / 10 minutes, more preferably 4 to 20 g / 10 minutes, and still more preferably 4 to 10 g / 10 minutes.

  As the foaming agent for obtaining the foam of the present invention, the decomposition of inorganic physical foaming agent, organic physical foaming agent, azodicarbonamide and the like is conventionally used for the production of polyethylene resin foams. A mold foaming agent can be used, and one or more foaming agents can be used. Examples of the inorganic foaming agent include oxygen, nitrogen, carbon dioxide, and air. Examples of the organic physical foaming agent include fats such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, isohexane, and cyclohexane. Group hydrocarbons, chlorohydrocarbons such as methyl chloride and ethyl chloride, and fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane. Of these, particularly preferred are those containing, as a main component, normal butane, isobutane, or a mixture thereof having good compatibility with polyethylene resins and good foamability.

  Moreover, it is preferable to add a cell regulator to the foamable polyethylene resin composition. As the bubble adjusting agent, either an organic type or an inorganic type can be used. Examples of the inorganic foam regulator include borate metal salts such as zinc borate, magnesium borate, borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate, and the like. Examples of the organic bubble regulator include sodium 2,2-methylenebis (4,6-tert-butylphenyl) phosphate, sodium benzoate, calcium benzoate, aluminum benzoate, and sodium stearate. Also, a combination of citric acid and sodium hydrogen carbonate, an alkali salt of citric acid and sodium hydrogen carbonate, or the like can be used as the bubble regulator. These bubble regulators can be used in combination of two or more.

  The amount of the foaming agent added is adjusted according to the type of foaming agent and the target density. Moreover, the addition amount of a bubble regulator is adjusted according to the target bubble diameter. That is, when isobutane is used as a foaming agent and a mixture of monosodium citrate and sodium hydrogen carbonate (“Finecell Master SSC-PO208K” manufactured by Dainichi Seika Kogyo Co., Ltd.) is used as a foam regulator, the amount of isobutane added is The amount is preferably 1 to 15 parts by weight per 100 parts by weight of the base resin, more preferably 1.5 to 12 parts by weight, and still more preferably 2 to 10 parts by weight. The amount is preferably 0.1 to 2 parts by weight per 100 parts by weight of the resin, more preferably 0.2 to 1.5 parts by weight, still more preferably 0.2 to 1.2 parts by weight. When talc is used, the amount is the same as described above.

  The foamable polyethylene resin composition has functions such as a nucleating agent, an antioxidant, a heat stabilizer, an antistatic agent, a conductivity-imparting agent, a weathering agent, an ultraviolet absorber, a flame retardant, etc. Additives, inorganic fillers and the like can be added.

  As mentioned above, although the conditions for obtaining the foam of this invention were demonstrated, it is not limited only to the said conditions.

  The molded body of the present invention can be obtained by a thermoforming method in which the foam is heated and softened and then molded using a mold composed of a male mold and / or a female mold. Examples of thermoforming methods for foams include vacuum forming and pressure forming, as well as free drawing forming, plug and ridge forming, ridge forming, matched mold forming, straight forming, drape forming, and reverse draw forming. , Air slip molding, plug assist molding, plug assist reverse draw molding and the like, and a molding method combining these. Such a thermoforming method is a preferable method because a molded body can be obtained continuously in a short time.

  The deep drawing ratio in the molded body of the present invention is preferably more than 0.45 and not more than 0.8, and more preferably 0.47 to 0.7. The deep drawing ratio employs a value obtained by obtaining the diameter of a circle corresponding to the opening area and dividing the depth by this diameter.

  Examples of uses of the molded article of the present invention include containers for fruit vegetables such as peaches, pears and tomatoes, insulated molded articles for kitchen sinks, insulated molded articles for lining the bathtubs of unit baths, and the like. The molded product of the present invention formed by thermoforming the above-mentioned non-crosslinked polyethylene resin foam for molding has no tears or irregularities called surface burns, has a good appearance, and tears into a molded product when deep drawn. Therefore, there is no possibility that the molded body will lose its shape or the stored product will spill out even if the molded body is transported without any deformation of the molded body, and in particular, a deep-drawn container for storing fruit vegetables and the like can be molded well.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Resins used in the following examples and comparative examples are as follows.
(1) LD1: Branched low density polyethylene “F102” (manufactured by Sumitomo Chemical Co., Ltd., density 922 g / L, MFR 0.3 g / 10 min, melt tension 179 mN, melting point 109 ° C., crystallization temperature 95 ° C.)
(2) LL1: linear low density polyethylene “AM567L” (manufactured by Nippon Polyethylene Co., Ltd., density 931 g / L, MFR 5.0 g / 10 min, melting point 125 ° C.)
(3) LL2: linear low density polyethylene “AM83NA” (manufactured by Nippon Polyethylene Co., Ltd., density 925 g / L, MFR 20.0 g / 10 min, melting point 123 ° C.)
(4) LL3: linear low density polyethylene “UJ790” (manufactured by Nippon Polyethylene Corporation, density 928 g / L, MFR 50.0 g / 10 min, melting point 124 ° C.)
(5) LL4: linear low density polyethylene “UF240” (manufactured by Nippon Polyethylene Co., Ltd., density 920 g / L, MFR 2.1 g / 10 min, melting point 123 ° C.)
(6) HD1: High density polyethylene “HJ590N” (manufactured by Nippon Polyethylene Co., Ltd., density 960 g / L, MFR 40.0 g / 10 min, melting point 133 ° C.)

Examples 1-5, Comparative Examples 1-4
Using an extruder (an internal diameter of 65 mm and a tandem extruder with an internal diameter of 90 mm) connected with a circular die (die lip diameter of 40 mm), the fatty acid compound A is used in 100 parts by weight of the resin composition having the composition shown in Table 1 in this extruder. 1.0 parts by weight of monostearic acid glyceride was added. Further, in Examples 1 to 5, fatty acid compounds B1 to B4 as fatty acid compounds B were added, respectively, as shown in Table 1. In addition, 70% by weight of normal butane and 30% by weight of isobutane as a foaming agent (but simply referred to as “butane” in the table) and a mixture of monosodium citrate and sodium bicarbonate as a foam regulator ("Finecell Master SSC-PO208K" manufactured by Dainichi Seika Kogyo Co., Ltd.) was blended at a ratio shown in Table 2 with respect to 100 parts by weight of the resin, and heated, melted and kneaded to obtain a foamable molten resin composition.

Next, this foamable molten resin composition was adjusted to the extrusion temperature shown in Table 2 and then introduced into an annular die and discharged from the die lip into the atmosphere at the discharge amount shown in Table 2 to form a cylinder. It was. At that time, the pressure of the die is adjusted to 5.7 to 8.2 MPa (G), and while taking up this cylindrical foam, the inner surface side thereof is placed on the peripheral surface of the cylindrical cooling device (diameter 150 mm, length 1500 mm). After cooling while passing along, it was cut open along the extrusion direction to obtain a sheet-like foam. Table 2 shows the ratio Q / P between the resin flow path cross-sectional area of the secondary breaker portion of the annular die: Q (mm ² ) and the discharge amount: P (kg / hr).
In addition, the shape of the secondary breaker of Examples 1-5 and Comparative Examples 1-4 used what the 350 cylindrical hole of diameter 3.5-4.1mm is arrange | positioned at equal intervals.
In the examples and comparative examples, as an adjustment method of the average bubble diameter in the extrusion direction: X (mm), the average bubble diameter in the width direction: Y (mm), and the average bubble diameter in the thickness direction: Z (mm), a bubble regulator was used. They were blended in the proportions shown in Table 2. As conditions for adjusting the bubble shape, the oil temperature control temperature (° C.) of the annular die, the discharge amount (kg / hr), the ratio of the discharge port diameter of the annular die and the diameter of the mandrel which is a cylindrical cooling device (table) Table 2 shows the blow rate and the take-up speed (m / min). In the present invention, the oil temperature adjustment temperature of the annular die refers to the die temperature of the die.

  As described above, the obtained sheet-like foam was defoamed with a heating press and a cooling press to obtain a non-foamed resin sheet, and the tensile elongation (%) was measured using this as a test piece. The obtained sheet-like foam was also degassed for MFR (g / 10 minutes) to obtain a measurement sample as a non-foamed resin. The results of heating tensile elongation (%) and MFR (g / 10 min) are shown in Table 3.

  The heat flux differential scanning calorific value was measured using the sheet-like foam molded by the above method, and the calorific value A (in the table) of the endothermic peak in the temperature range of 40 to 112 ° C. obtained from the DSC curve obtained thereby. In the table, the heat quantity B is simply “heat quantity A”), the heat quantity B of the endothermic peak in the temperature range of 112 ° C. or higher (simply referred to as “heat quantity B” in the table) and their ratio, the average cell diameter X in the extrusion direction, Table 3 shows the ratio of Z to X and the ratio of Z to Y in the average bubble diameter Y in the direction and the average bubble diameter Z in the thickness direction. Table 4 shows the apparent density, thickness, open cell ratio, and moldability of the obtained sheet-like foam. Further, the results of testing the moldable temperature range and deep drawability of the sheet-like foam are shown in Table 4 together with the appearance evaluation.

表中のＡ１、Ｂ１〜Ｂ４は、以下の通り。
Ａ1：脂肪酸エステル系 モノステアリン酸グリセライド
Ｂ１：脂肪酸アミド系 ステアリン酸アミド（炭素原子：１８個）
Ｂ２：脂肪酸アミド系 エルカ酸アミド（炭素原子：２２個）
Ｂ３：脂肪酸エステル系 ソルビタントリべへネート
Ｂ４：脂肪酸エステル系 ポリアジピン酸ペンタエリストールステアレート (Table 1)

A1, B1 to B4 in the table are as follows.
A1: Fatty acid ester type monostearic acid glyceride B1: Fatty acid amide type stearic acid amide (18 carbon atoms)
B2: Fatty acid amide erucic acid amide (22 carbon atoms)
B3: Fatty acid ester-based sorbitan tribehenate B4: Fatty acid ester-based polyadipic acid pentaerythrole stearate

(Table 2)

(Table 3)

(Table 4)

  Values obtained by the measurement method described above were adopted for the heat quantity, bubble shape, apparent density, thickness, and open cell ratio of the endothermic peak in the DSC curve.

Test of forming range in formability of Table 4 Using a single-shot vacuum forming machine (manufactured by Asano Laboratory Co., Ltd .: FSK type), the outer dimension is a rectangular shape of 290 mm × 290 mm, the shape of the opening is an ellipse, the major axis is 80 mm, the minor axis The mold surface temperature is adjusted to 80 ° C. and the surface temperature of the sheet-like foam is set to 118 to 124 ° C. by using a mold having nine hemispherical concave portions of 75 mm, a depth of 35 mm, and a deep drawing ratio of 0.45. The following evaluation was made according to the width of the heating time of the sheet-like foam from which a good molded product having no tearing, uneven thickness, and no surface burn was obtained.
The heating time of the sheet-like foam exceeds 6 seconds.
The width of the heating time of the sheet-like foam is 3 seconds or more and 6 seconds or less.
The width of the heating time of the sheet-like foam is 1 second or more and less than 3 seconds ... △
The width of the heating time of the sheet-like foam is less than 1 second ...

Deep drawability test of Table 4 Using a single vacuum forming machine (manufactured by Asano Laboratories: FSK type), the outer shape is a rectangular shape of 290 mm × 290 mm, the shape of the opening is circular, the diameter is 105 mm, the depth is 53 mm, the depth When the mold surface temperature is adjusted to 80 ° C. and the surface temperature of the sheet-like foam is heat-molded at 118 to 124 ° C. by a deep drawing mold having eight hemispherical concave portions with a drawing ratio of 0.5. In addition, the following evaluation was made according to the occurrence of tearing.
There is no tear in the molded body ...
Minor tears occurred on the most extended side of the molded body ... △
Many large tears occurred in the entire molded body ...

  The foams obtained in the examples and comparative examples were measured for the insoluble content in boiling xylene by the measurement method described above, and the result was 0% by weight.

  As is clear from the test results of the above examples and comparative examples, all of the examples of the present invention have a wide moldable temperature range, good deep drawability, and the foam has no surface irregularities. It was good and was shown to be excellent in thermoformability. On the other hand, Comparative Examples 1 to 4 are inferior to the examples of the present invention in both the moldable range and the deep drawability. In particular, in Comparative Examples 2 to 4, a large tear occurs in the entire molded body. did. Moreover, in Comparative Example 3 and Comparative Example 4, irregularities were formed on the surface, and a good foam was not obtained in appearance. In Comparative Example 3, the drawdown was larger during thermoforming than in the Example. Moreover, in Comparative Example 4, when thermoforming, the elongation of the sheet-like foam was worse than that in Examples.

It is an example of the DSC curve obtained by the heat flux differential scanning calorimetry of the foam of the present invention. It is explanatory drawing which shows an example of how to draw a baseline. It is an example of the DSC curve obtained by the heat flux differential scanning calorimetry of the foam corresponding to a comparative example.

Claims (5)

  A non-crosslinked polyethylene resin extruded foam obtained by extruding and foaming a melt foamable resin composition containing a foaming agent in a polyethylene resin composition, wherein the polyethylene resin composition constituting the foam is 120 ° C. The tensile elongation during heating for 60 seconds is 240 to 350%, the MFR is 0.5 to 2.5 g / 10 minutes, the apparent density of the foam is 15 to 460 g / L, the thickness is 1 to 10 mm, and continuous. A non-crosslinked polyethylene-based resin extruded foam having a bubble ratio of 30% or less and having at least two melting calorie peaks on a DSC curve obtained by differential scanning calorimetry of the foam.   The non-crosslinked polyethylene resin extruded foam according to claim 1, comprising a heat elongation modifier comprising a fatty acid compound.   The non-crosslinked polyethylene resin extruded product according to claim 2, wherein the fatty acid compound is a mixture of a fatty acid compound A comprising a polyhydric alcohol and a partial ester of a fatty acid and a fatty acid compound B other than the fatty acid compound A. Foam.   The non-crosslinked polyethylene resin extruded foam according to claim 3, wherein the fatty acid compound B is a fatty acid amide compound having 12 to 24 carbon atoms. The molded object formed by thermoforming the non-crosslinked polyethylene resin extrusion foam in any one of the said Claims 1-4.

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