JP2005194433A - Manufacturing method of polyolefin resin foamed body and polyolefin resin foamed body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a polyolefin resin foamed body which, when used as a packaging material, has least possibility of contaminating the surface of a contacting material, which excels in appearance and which shows antistatic characteristics uniform over the entire surface, and to provide the polyolefin resin foamed body. <P>SOLUTION: The manufacturing method of the polyolefin resin foamed body comprises kneading a polymer type antistatic agent whose crystallization temperature is ≤110°C and whose melt viscosity at the measuring temperature of 190°C and the shear rate of 100 sec<SP>-1</SP>is 80-1,000 Pa×s, a polyolefin resin, and a physical foaming agent in an extruder to form an expandable polyolefin resin melt and subjecting the expandable polyolefin resin melt to extrusion foaming to obtain the polyolefin resin foamed body. The polymer type antistatic agent is added in an amount of 2-8 pts.wt. based on 100 pts.wt. of the polyolefin resin, and the extrusion foaming is performed so that the apparent density of the foamed body may be 65 g/L or lower. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing an antistatic polyolefin resin foam and an antistatic polyolefin resin foam, and particularly to a method for producing a polyolefin resin foam having excellent antistatic performance and low apparent density, and a polyolefin type. The present invention relates to a resin foam.

  Conventionally, foams made of polyolefin resin have been widely used as suitable cushioning materials, packaging materials, and the like because they are rich in flexibility and buffering properties and are difficult to damage a packaged body. In particular, foams made of polyethylene resin have been widely used because they can be easily highly foamed and can be produced at low cost. However, since these foams have the undesirable property of being easily dusted by the action of static electricity, antistatic polyolefin resin foams having improved conductivity using an antistatic agent have been developed and used. Has been.

  Conventionally, so-called surfactant type antistatic agents have been widely used because they are available at low cost. Examples of the surfactant type include glycerin fatty acid ester, polyoxyethylene alkylamine, alkyldiethanolamide and the like (for example, see Patent Document 1).

  However, the antistatic effect when the surfactant type antistatic agent is used is manifested by the antistatic agent bleeding out from the resin to the surface and adsorbing moisture in the air. Therefore, there is a problem that the antistatic effect is hardly exhibited in an environment with relatively low humidity, particularly in winter. On the other hand, although the antistatic effect is manifested in a relatively high humidity environment, especially in summer, the surface of the packaged body becomes sticky or whitens due to the migration of the antistatic agent that has absorbed moisture to the packaged product. Such a phenomenon occurs, and the surface contamination of the packaged body is caused.

JP-A-9-169072 (pages 3 to 4, paragraph number 0016)

  The present invention has been made in view of the above problems, and when used as a packaging material, it has a very low possibility of contaminating the surface of the other party to be contacted, has an excellent appearance, and has uniform antistatic properties over the entire surface. An object of the present invention is to provide a method for producing a polyolefin-based resin foam in which is exhibited, and a polyolefin-based resin foam.

In order to solve the above-described problems, the present inventors tried to produce a foam by supplying a polymer type antistatic agent and a polyolefin resin to an extruder. At this time, it was found that by setting the apparent density of the foam to a specific value, the antistatic performance can be realized with a surprisingly small amount of the polymer antistatic agent. That is, according to this invention, the manufacturing method of polyolefin resin foam and the polyolefin resin foam which are excellent in the antistatic property shown below are provided.
[1] Polymer antistatic agent having a crystallization temperature of 110 ° C. or less, a measurement temperature of 190 ° C., and a melt viscosity of 80 to 1000 Pa · s at a shear rate of 100 sec ⁻¹ , a polyolefin resin, and a physical foaming agent And kneading in an extruder to form a foamable polyolefin resin melt, and extruding and foaming the foamable polyolefin resin melt to obtain a polyolefin resin foam, 2. A polyolefin resin characterized by adding 2 to 8 parts by weight of a polymeric antistatic agent to 100 parts by weight of a polyolefin resin and extrusion-foaming so that the apparent density of the foam is 65 g / L or less A method for producing a foam.
[2] The method for producing a polyolefin resin foam according to [1], wherein the polyolefin resin is a polyethylene resin having a melt tension of 30 to 400 mN at 190 ° C.
[3] The method for producing a polyolefin resin foam according to [1], wherein the polyolefin resin is a polypropylene resin having a melt tension at 230 ° C. of 30 to 400 mN.
[4] Contains 8% by weight or less of a polymer antistatic agent, has an apparent density of 15 to 65 g / L, and has a surface resistivity of 1 × 10 ⁸ to 1 × after ultrasonic cleaning using ethanol. A polyolefin-based resin foam that is 10 ¹³ (Ω) and has an average cell diameter satisfying the following formulas (1), (2), and (3):
0.35 ≦ Z / X ≦ 1.2 (1)
0.35 ≦ Z / Y ≦ 1.2 (2)
0.2 ≦ Z ≦ 1.4 (3)
(However, X, Y, and Z are 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).)
[5] The polyolefin resin foam according to [4], wherein the foam has an open cell ratio of 65% or less.

According to the method for producing a polyolefin resin foam of the invention according to claim 1 of the present invention, the crystallization temperature is 110 ° C. or lower, the measurement temperature is 190 ° C., and the melt viscosity at a shear rate of 100 sec ⁻¹ is 80 to 1000 Pa. -2-8 parts by weight of the polymer type antistatic agent which is s is added to 100 parts by weight of the polyolefin resin, and the foam is extruded and foamed so that the apparent density of the foam is 65 g / L or less. When used as an antistatic foam, it is extremely unlikely to contaminate the surface of the mating contact, has an excellent appearance, exhibits uniform antistatic properties over its entire surface, and has flexibility and buffering properties. can do.
According to the method for producing an antistatic polyolefin resin foam of the invention according to claim 2 of the present invention, the polyolefin resin is a polyethylene resin having a melt tension of 30 to 400 mN at 190 ° C. A low foam can be easily obtained, and an antistatic polyethylene resin foam excellent in appearance can be obtained with little reduction in rigidity due to open cell formation.
According to the method for producing an antistatic polyolefin resin foam of the invention according to claim 3 of the present invention, since the polyolefin resin is a polypropylene resin having a melt tension of 30 to 400 mN at 230 ° C., the apparent density is low. A foam can be easily obtained, and an antistatic polypropylene resin foam excellent in appearance can be obtained with little reduction in rigidity due to open cell formation.
According to the invention related to claim 4 of the present invention, the surface specific resistivity after ultrasonic cleaning using ethanol containing a polymer type antistatic agent in an amount of 8 wt% or less, an apparent density of 15 to 65 g / L, and ethanol. Is set to 1 × 10 ⁸ to 1 × 10 ¹³ (Ω), and the average cell diameter satisfying a specific relational expression makes it extremely unlikely to contaminate the surface of the contact partner when used as a packaging material. It is possible to provide a foam having excellent appearance, uniform antistatic properties over its entire surface, and flexibility and buffering properties.
According to the invention concerning Claim 5 of this invention, even if the thickness of a foam is thin, the polyolefin resin foam excellent in the buffer property as a packaging use can be provided.

Hereinafter, a method for producing a polyolefin resin foam of the present invention (hereinafter also simply referred to as “foam”) will be described in detail.
As a manufacturing method of the foam of this invention, the well-known manufacturing method which attached T die, circular die, etc. to the front-end | tip of an extruder is mentioned, for example. Among them, a circular die is preferable because a foam sheet or foam plate having a width of 1000 mm can be easily obtained, and the foamable polyolefin resin melt is uniformly stretched, thereby exhibiting permanent antistatic performance. As shown in FIG. 1, for example, polyolefin resin (I), polymer antistatic agent (II) and physical foaming agent (III) are added and kneaded in an extruder to obtain foaming properties. Form a polyolefin resin melt (IV), adjust the temperature of the expandable polyolefin resin melt (IV) to an appropriate foaming temperature, and then extrude and foam to form a cylindrical foam. Thereby, a foam (V) is obtained.

  The polyolefin resin used in the present invention is a resin having an olefin component unit of 50 mol% or more. Examples of the polyolefin resin include a polyethylene resin and a polypropylene resin. The polyolefin-based resin is preferably used because of its low surface hardness and excellent flexibility and excellent surface protection for the package.

  Examples of the polyethylene-based resin include resins having an ethylene component unit of 50 mol% or more, ethylene homopolymers such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, and ethylene-vinyl acetate copolymer. Polymer, ethylene-vinyl acetate copolymer and high density polyethylene resin mixture, ethylene-propylene copolymer, ethylene-propylene-butene-1 copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer Examples thereof include polymers, ethylene-based copolymers such as ethylene-4-methylpentene-1 copolymer, ethylene-octene-1 copolymer, and mixtures of two or more thereof.

Among these polyethylene resins, those having a main component of a polyethylene resin having a density of 935 g / L or less are preferable. Specifically, it is preferable to use low-density polyethylene, linear low-density polyethylene, or the like, and low-density polyethylene with good foamability is more preferable.
In addition, a polyethylene resin having a density of 935 g / L or less as a “main component” means that the content of the polyethylene resin is 50% by weight or more of the total weight of the foam. The lower limit of the density of the polyethylene resin is 910 g / L.

  Examples of the polypropylene resin used in the present invention include a propylene polymer or a copolymer with another olefin copolymerizable with propylene. Examples of other olefins copolymerizable with propylene include ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1- Examples thereof include α-olefins having 2 to 10 carbon atoms such as heptene and 3-methyl-1-hexene. The copolymer may be a random copolymer or a block copolymer, and may be not only a binary copolymer but also a ternary copolymer. These polypropylene resins can be used alone or in admixture of two or more.

  When the above copolymer is used as a base resin constituting a foam, the copolymer may contain an olefin as a copolymer component in a proportion of 25% by weight or less, particularly 15% by weight or less. preferable. The preferred lower limit of the copolymer component contained in the copolymer is 0.3% by weight.

Among the polypropylene resins used as the base resin constituting the foam, a resin suitable for extrusion foaming is preferably a polypropylene resin having a higher melt tension than a general polypropylene resin. Specifically, for example, as described in JP-A-7-53797, (1) polypropylene having a branching index less than 1 and significant strain hardening elongation viscosity, (2) (a) Z average The molecular weight (Mz) is 1.0 × 10 ⁶ or more, or the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 3.0 or more, (b) and Polypropylene resin using polypropylene having an equilibrium compliance J ₀ of 1.2 × 10 ⁻³ Pa ⁻¹ or more or a shear strain recovery Sr / S per unit stress of 5 m ² / N or more is preferable.

  In the present invention, (3) a compound containing a radical polymerizable monomer such as styrene and a radical polymerization initiator or an additive is melted at a decomposition temperature of the radical polymerization initiator when the polypropylene resin melts. It may be a polypropylene resin modified by melt kneading, or (4) a modified polypropylene resin obtained by melt kneading a polypropylene resin, an isoprene monomer and a radical polymerization initiator. Further, among these base resins, those having a low proportion of insoluble components are preferable. The ratio of the insoluble component is the foamed sample, the sample is placed in xylene at 145 ° C. and boiled for 8 hours, then filtered quickly with a 100 mesh wire mesh, and then the boiling xylene insoluble component remaining on the wire mesh is removed. After drying in an oven at 20 ° C. for 24 hours, the weight G (g) of the insoluble component is measured, and the proportion of the insoluble component determined by the following formula (4) is 0 to 10% by weight. Is preferably 0 to 5% by weight, more preferably 0 to 2% by weight. The lower the proportion of insoluble components, the better the recyclability and the more preferable from the viewpoint of cost reduction.

Ratio of insoluble component after drying (% by weight) = [G (g) / sample weight (g)] × 100
……… (4)

In the present invention, extrusion foaming is performed so that the surface resistivity of the obtained foam is 1 × 10 ⁸ to 1 × 10 ¹³ (Ω).
For this purpose, 2 to 8 parts by weight of a polymer antistatic agent is added to 100 parts by weight of the polyolefin resin. When the addition amount of the polymer type antistatic agent exceeds 8 parts by weight, foaming is inhibited, and a foam having a low open cell density and a low density cannot be obtained. A foam having a high open cell ratio is inferior in buffering property, and further, its use is limited because the bubbles are coarse. From the above viewpoint, 7 parts by weight or less is preferable, and 6.5 parts by weight or less is more preferable.
On the other hand, when the amount is less than 2 parts by weight, the surface resistivity cannot be 1 × 10 ¹³ (Ω) or less. Therefore, the addition amount of the polymer type antistatic agent is preferably 3 parts by weight or more, more preferably 3.8 parts by weight or more.

  In this specification, the surface resistivity of the obtained foam is the surface resistivity after ultrasonic cleaning using ethanol, and is measured according to the description described later.

In the present invention, by adding a polymer type antistatic agent to a polyolefin-based resin and extrusion foaming so that the apparent density of the foam is 65 g / L or less, the surface specific resistivity of the foam obtained is 1 × 10 ⁸ to 1 × 10 ¹³ (Ω). The effect of the polymer-type antistatic agent does not depend on the standing time or humidity conditions, and the surface resistivity of the foam can be set to 1 × 10 ⁸ to 1 × 10 ¹³ (Ω) immediately after production.

The polymer antistatic agent is made of a resin having a surface resistivity of less than 1 × 10 ¹² Ω.
Specifically, an ionomer resin containing an alkali metal selected from the group consisting of potassium, rubidium, and cesium as a metal ion, and a hydrophilic resin mainly composed of polyetheresteramide or polyether. In addition, the polymer antistatic agent has improved compatibility with the polyolefin resin constituting the foam, and has an excellent antistatic effect, and also has an effect of suppressing deterioration of physical properties due to the addition of the antistatic agent. Therefore, it is more preferable to use a block copolymer of the same type of polyolefin resin as the polyolefin resin.

Particularly preferred polymer type antistatic agents are ionomers in which part or all of the ethylene-unsaturated carboxylic acid copolymer is neutralized with an alkali metal selected from the group consisting of potassium, rubidium and cesium, and The composition described in -278985 is mentioned.
The composition described in JP-A-2001-278985 includes a block of polyolefin (a) and a block of hydrophilic polymer (b) having a volume resistivity value of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω · cm, It is a block polymer (A) having a number average molecular weight (Mn) of 2000 to 60000 having a structure in which repetitive bonding is repeated. The block (a) and the block (b) have a structure in which they are alternately and repeatedly bonded through at least one bond selected from an ester bond, an amide bond, an ether bond, a urethane bond, and an imide bond. is there.
The polymer type antistatic agent preferably used in the present invention will be described in detail later.

  In the present invention, the foam is formed by extrusion foaming so that the apparent density of the obtained foam is 65 g / L or less. As described above, when the polymer type antistatic agent is oriented in the process of bubble growth during foaming by highly foaming, the antistatic property can be dramatically improved even with a small addition amount. From the above viewpoint, the apparent density is preferably 61 g / L or less, more preferably 51 g / L or less, and still more preferably 44 g / L or less. On the other hand, the lower limit of the apparent density is preferably 15 g / L or more, more preferably 18 g / L or more, and further preferably 21 g / L or more, from the viewpoint that the physical strength of the foam may be lowered.

  The thickness of the foam in the present invention is preferably from 0.3 mm to 30 mm, more preferably from 0.3 mm to 20 mm, and even more preferably from 0.3 mm to 10 mm from the viewpoint of excellent buffering properties. In particular, when the surface of the package is covered and packaged, the thickness is preferably 0.3 mm to 10 mm. If the thickness is less than 0.3 mm, the foam may have insufficient rigidity and cushioning properties. From this viewpoint, the thickness of the foam is preferably 0.5 mm or more, and more preferably 0.8 mm or more. On the other hand, when the thickness of the foam is too thick, there is a possibility that handling may be bad when packaging an object to be packaged, and it may be difficult to form the same shape as a mold when thermoforming. Therefore, the thickness of the foam is preferably 8 mm or less, and more preferably 6 mm or less.

  In the case of a foam having a thickness exceeding 30 mm, a laminated foam obtained by adhering the foam to two or more layers can be obtained. Moreover, even if it is a case where it is a case where it is set as a foam less than 30 mm, it is good also as a laminated foam formed by adhere | attaching two or more layers. When two or more laminated foams are used, if the same foam can be laminated, foams having different thicknesses, bubble diameters, and apparent densities, and further color, base resin, functional additives, etc. Different types of foams can be laminated.

In addition, the thickness of the foam as used in this specification means the thickness which does not contain a resin layer, when providing a polyolefin-type resin layer on at least one side so that it may mention later.
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. Further, when a polyolefin resin layer is provided on at least one surface of the foam, the thickness of the foam and the thickness of the resin layer are measured at each point photographed as described above, and the arithmetic average value of the obtained measured values Are the thickness of the foam and the thickness of the resin layer.

  In order to make the foam difficult to break, it is preferable to provide a polyolefin resin layer having a thickness of 5 μm or more on at least one side, preferably 8 μm or more, and more preferably 12 μm or more. On the other hand, it is necessary to increase the thickness of the resin layer further in order not to reduce the antistatic effect. However, if the thickness is too large, the weight may increase and the lightness may be deteriorated, so the thickness of the resin layer is 150 μm or less. Is preferable, and 100 μm or less is more preferable. The polyolefin resin layer can be formed by a known method such as laminating a polyolefin resin film on a foam.

  The polyolefin resin constituting the polyolefin resin layer preferably has a melt flow rate (MFR) of 1 g / 10 min or more from the viewpoint of improving the appearance of the foam. On the other hand, although there is no restriction | limiting in particular in the upper limit of MFR, Usually, it is 20 g / 10min or less.

According to JIS K7210 (1976), the melt flow rate (MFR) is 190 ° C. and the load is 21.17 N when the polyolefin resin is a polyethylene resin, and the polyolefin resin is a polypropylene resin. , 230 ° C., load 21.17N.
The test piece is made of raw material pellets, and the measurement temperature is based on the melting temperature at the time of melt kneading.

  Examples of the polyolefin resin constituting the resin layer include a polyethylene resin and a polyolefin resin. Examples of the polyethylene resin include ethylene component units of 50 mol% or more, and ethylene homopolymers such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene -Propylene copolymer, ethylene-propylene-butene-1 copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-octene -1 copolymer and the like, and a mixture of two or more of these.

  1.5-15 g / 10min is preferable and, as for MFR of the polyethylene-type resin which comprises the said resin layer, 2-10 g / 10min is more preferable. The measurement conditions for the MFR are as described above.

  Examples of the polypropylene resin constituting the resin layer include general-purpose polypropylene resins in addition to the polypropylene resin constituting the foam described above. In that case, MFR is preferably 1.5 to 15 g / 10 min, and more preferably 2 to 10 g / 10 min. The measurement conditions for the MFR are as described above.

  The polyolefin resin constituting the polyolefin resin layer is a styrene resin such as polystyrene, an elastomer such as ethylene propylene rubber, a butene resin such as polybutene, a polychlorinated resin, and the like within a range not inhibiting the purpose and effect of the foam of the present invention. A vinyl chloride resin such as vinyl 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.

  The above-mentioned polyolefin resin layer is composed of, for example, a functional additive such as a nucleating agent, an antioxidant, a heat stabilizer, a weathering agent, an ultraviolet absorber, a flame retardant, and the like, and a group consisting of potassium, rubidium and cesium as metal ions. Various additives such as an ionomer resin containing a selected alkali metal, a permanent antistatic agent used in the above-mentioned foam, and an inorganic filler may be contained.

The method for measuring the apparent density of the foam in this specification is as follows.
First, the thickness of the foam (E) is measured in advance as follows.
The foam is cut perpendicularly to the direction perpendicular to the extrusion direction, and the thickness of the cut surface is photographed at 10 points in the width direction at regular intervals with a microscope, and the thickness of the foam at each photographed point is measured and obtained. The arithmetic average value of the measured values is taken as the thickness of the foam.
Next, the basis weight of the foam (E) is measured. The basis weight of the foam (E) is obtained by cutting a test piece having a length of 25 mm × width 25 mm × foam thickness, measuring the weight (g) of the test piece, multiplying the weight by 1600, and converting the unit. Is obtained (g / m ² ).

A value obtained by dividing the basis weight (g / m ² ) of the foam by the thickness (mm) of the foam is converted into a unit, and the apparent density (g / L) of the foam is obtained.
When there is a polyolefin-based resin layer on at least one surface of the foam, the thickness and basis weight of the polyolefin-based resin layer are measured, and the basis weight (g / m ² ) of the polyolefin-based resin layer is the thickness measuring method described above. This is obtained by multiplying the thickness of the resin layer obtained by the above by the density of the base resin constituting the resin layer and performing unit conversion. However, if it contains a large amount of inorganic material, the resin layer is removed from the foam, the basis weight of the foam is obtained in the same manner as the basis weight of the foam, and foamed with a polyolefin resin layer laminated on at least one side The value obtained by subtracting the basis weight of the foam from the basis weight of the body is adopted as the basis weight of the resin layer.

As a method of bringing the apparent density of the foam into the above range, there is a method of adjusting the addition amount of the physical foaming agent, the addition amount of the bubble adjusting agent, and the foaming temperature. Examples of the foaming agent include the following physical foaming agents.
Examples of the physical foaming agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, isohexane and cyclohexane, chlorinated hydrocarbons such as methyl chloride and ethyl chloride, 1,1,1 , 2-tetrafluoroethane, organic physical foaming agents such as fluorinated hydrocarbons such as 1,1-difluoroethane, and inorganic foaming agents such as oxygen, nitrogen, carbon dioxide and air. These physical foaming agents can be used in combination of two or more. Among these, when a polyethylene resin is selected as the polyolefin resin, an organic foaming agent is preferable from the viewpoint of compatibility with the resin and foaming properties, among which normal butane, isobutane, or a mixture thereof is the main component. Is preferred.

  Moreover, when manufacturing manufacture of a foam, a bubble regulator is added. 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. A combination of citric acid and sodium bicarbonate, an alkali salt of citric acid and sodium bicarbonate, or the like can also 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 apparent density. The amount of the bubble regulator added is mainly adjusted according to the target bubble diameter. In particular, in the present invention, the amount of foaming agent injected is important because the stretching effect due to the formation of the bubble film is related to antistatic properties. That is, when a butane mixture of 30% by weight of isobutane and 70% by weight of normal butane is used as the blowing agent, the amount of butane mixture added is 4 to 35 parts by weight, preferably 5 to 30 parts by weight per 100 parts by weight of the polyolefin resin. More preferably, it is 6 to 25 parts by weight. Moreover, as a bubble regulator, for example, when a master batch prepared with a blending amount of 11.8 parts by weight of talc and 5.9 parts by weight of sodium citrate with respect to 100 parts by weight of polyethylene is used, The amount is 0.3 to 10 parts by weight, preferably 0.5 to 5 parts by weight, per 100 parts by weight of the polyolefin resin.

The polymer antistatic agent used in the present invention has a crystallization temperature of 110 ° C. or lower and a melt viscosity at 190 ° C. of 80 to 1000 Pa · s.
When the crystallization temperature exceeds 110 ° C., kneading at the time of melting becomes insufficient, and the antistatic effect is hardly exhibited. In particular, when the crystallization temperature of the polymer antistatic agent is higher than the crystallization temperature of the polyolefin resin, if the crystallization temperature of the antistatic agent is too high, crystallization occurs inside the extruder and hinders foaming. There is.
However, the lower limit of the crystallization temperature is about 60 ° C. If the crystallization temperature is too low, the physical properties of the resin composition are lowered, which is not preferable.

  The appropriate temperature of the melt (IV) in the extruder 11 is a temperature at which a low-density foam can be easily obtained. Specifically, it is [crystallization temperature + 5 ° C.] or more and [crystallization temperature + 30 ° C.] or less of the olefin resin, which is preferable from the viewpoint of improving the open cell ratio of the foam and suppressing shrinkage of the obtained foam.

  In the foamable polyolefin resin melt (IV), the polymer antistatic agent (II) can be uniformly dispersed to form a conductive network. The balance of viscosity during kneading of the resin melt (IV) is important. Specifically, when selecting the polyolefin resin (I) and the polymer antistatic agent (II) of the foamable polyolefin resin melt (IV), it is necessary to satisfy the following relationship between the crystallization temperature and the melt viscosity. There is.

Tb <[Ta + 30 ° C.] (5)
In the formula, Tb is the crystallization temperature (° C.) of the polymer antistatic agent (II), and Ta is the crystallization temperature (° C.) of the polyolefin resin (I) used for the foam. This is because when the relationship between the crystallization temperatures of the polymer antistatic agent (B) and the polyolefin resin (I) does not satisfy the above formula, that is, when Tb is higher than [Ta + 30 ° C.], a foam is produced. When doing so, the polymer antistatic agent (II) may crystallize and become a lump, and the surface of the foam may be uneven. Accordingly, it is important that the polymer antistatic agent (II) is sufficiently melted at the melting temperature of the polyolefin resin layer (A).

  In this specification, the value measured with the following method is employ | adopted for the crystallization temperature of polyolefin resin (I) and polymer type antistatic agent (II).

In this specification, the value measured by a method based on JIS K7122 (1987) is adopted as the crystallization temperature of the polymer antistatic agent. Details are as follows.
2 to 4 mg of a sample is collected, and the temperature is raised from room temperature (about 23 ° C.) to 230 ° 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. In this case, in the curve obtained during cooling, the temperature at the peak apex is defined as the crystallization temperature. When two or more exothermic peaks appear, the temperature at the apex of the largest exothermic peak is defined as the crystallization temperature. However, when there are a plurality of large exothermic peak areas, the peak of the highest exothermic peak among them is defined as the crystallization temperature.

  The melt viscosity at 190 ° C. of the polymer antistatic agent of the present invention is 80 to 1000 Pa · s. Such a polymer antistatic agent having a melt viscosity can be sufficiently kneaded, so that a preferable conductive network can be formed. From the above viewpoint, 150 to 800 Pa · s is preferable, and 150 to 500 Pa · s is more preferable. As a result, when combined with a configuration in which the apparent density of the foam is 65 g / L or less, an excellent antistatic function is exhibited in the foam even at a low addition amount.

  The melt viscosity (Ma) at 190 ° C. of the polyolefin resin used in the present invention is preferably 250 to 6000 Pa · s, and more preferably 300 to 5000 Pa · s. If the melt viscosity (Ma) exceeds 6000 Pa · s, the load applied to the extruder becomes too high, and the control during extrusion becomes difficult, and the elongation of the resin at the time of foaming becomes insufficient, and the foam has a good appearance. The body may not be obtained. On the other hand, if the melt viscosity (Ma) is less than 250 Pa · s, the kneadability with the polymer antistatic agent is deteriorated, the uniform dispersibility of the polymer antistatic agent is adversely affected, and the antistatic effect is reduced. There is a fear.

  When a polyethylene resin is selected as the polyolefin resin, it is preferable to use a resin having a melt viscosity at 190 ° C. of 300 to 1600 Pa · s, more preferably 700 to 1500 Pa · s. In the case of a foam made of a polyethylene resin, it is often used for applications that require buffering properties, and the bubbles are also fine. However, since the melt viscosity of the polymer antistatic agent is not suitable for foaming, it is preferable to select a polyethylene resin having a high melt tension in order to compensate for it.

  When a polypropylene resin is selected as the polyolefin resin, it is preferable to use a resin having a melt viscosity at 190 ° C. in the range of 2000 to 6000 Pa · s, more preferably 3000 to 5500 Pa · s, and 4000 to 5000 Pa · s. It is particularly preferable to use a high viscosity s. Examples of such high viscosity polypropylene resins include high melt tension type polypropylene resins as described above.

The melt viscosity in this specification is measured as follows.
A Leobis 2100 manufactured by Thiast Co., Ltd. is used as a measuring device, and measurement is performed under conditions of an orifice diameter of 1 mm, an orifice length of 10 mm, a measurement temperature of 190 ° C., and a shear rate of 100 sec ⁻¹ .
The test piece is made of raw material pellets, and the measurement temperature is based on the melting temperature at the time of melt kneading. Therefore, it is preferable from the viewpoints of kneadability and uniform dispersibility that the melt viscosity at 190 ° C. of the polymer type antistatic agent and the polyolefin resin is within the above range.

  In the present invention, in order to exert the effect at a low addition amount of the polymer antistatic agent, in addition to the stretching effect by foaming, the relationship between the melt viscosity at 190 ° C. of the polymer antistatic agent and the polyolefin resin is It is preferable to control to satisfy the following formula (6).

Ma> Mb (6)
However, in the formula (6), Ma is the melt viscosity (Pa · s) at 190 ° C. of the polyolefin resin, and Mb is the melt viscosity (Pa · s) at 190 ° C. of the polymer type antistatic agent.

  As shown in the above formula (6), by making the melt viscosity (Ma) of the polyolefin resin higher than the melt viscosity (Mb) of the polymer antistatic agent, predetermined antistatic properties are exhibited. It becomes easy. On the other hand, when the melt viscosity (Ma) of the polyolefin resin is the same as or lower than the melt viscosity (Mb) of the polymer antistatic agent, it becomes difficult to form a conductive network structure of the polymer antistatic agent. There is a fear.

The relationship between Ma and Mb is preferably such that Mb is less than 0.90Ma (0.90Ma> Mb) from the viewpoint of exhibiting antistatic properties with a small amount of the polymeric antistatic agent added. ), More preferably less than 0.70 Ma (0.70 Ma> Mb).
On the other hand, the lower limit is that Mb is preferably greater than 0.10 Ma (Mb> 0.10 Ma), and more preferably, Mb is greater than 0.15 Ma, from the viewpoint that predetermined antistatic properties can be exhibited. > 0.15 Ma).

  As the polyethylene resin used in the present invention, those having a melt tension at 190 ° C. of 30 mN to 400 mN are preferable. When the melt tension at 190 ° C. is less than 30 mN, there is a possibility of reduction in magnification or open cell formation. On the other hand, when the melt tension at 190 ° C. exceeds 400 mN, the viscosity of the resin increases, and the load may be high during extrusion. The melt tension at 190 ° C. of the polyethylene resin is more preferably 35 mN or more, and even more preferably 40 mN or more, from the viewpoint that it is easy to obtain a low-density foam. Moreover, from the viewpoint that it is easy to obtain a foam having a low open cell ratio, the melt tension at 190 ° C. of the polyethylene resin is more preferably 300 mN or less, and further preferably 250 mN or less. The reason for measuring at 190 ° C. is that the temperature correlates with the state when the melt physical properties are foamed.

  The polypropylene resin used in the present invention preferably has a melt tension at 230 ° C. of 30 mN to 400 mN. When the melt tension at 230 ° C. is less than 30 mN, there is a possibility of reduction in magnification or open cell formation. On the other hand, if the melt tension at 230 ° C. exceeds 400 mN, the viscosity of the resin increases, and the load may be high during extrusion. The melt tension at 230 ° C. of the polypropylene resin is more preferably 30 mN or more, and further preferably 50 mN or more, from the viewpoint that it is easy to obtain a low-density foam. Moreover, from the viewpoint of easily obtaining a foam having a low open cell ratio, the melt tension at 230 ° C. of the polypropylene resin is more preferably 300 mN or less, further preferably 250 mN or less. In addition, the reason for measuring at 230 degreeC is because the temperature has a correlation with the state at the time of a melt physical property foaming.

In the present specification, the melt tension (sometimes referred to as melt tension or MT) of a polyolefin resin can be measured by, for example, a melt tension tester type II manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, when the polyolefin resin to be measured is a polyethylene resin, the measurement is performed as follows.
Using a melt tension tester having a nozzle with a nozzle diameter of 2.095 mm and a length of 8 mm, the resin was extruded from the nozzle under the conditions of a resin temperature of 190 ° C. and an extrusion piston speed of 10 mm / min. After hanging on a 45 mm diameter tension detection pulley, gradually increase the scraping speed at a rate of about 5 rpm / second (stretching acceleration of the string-like object: 1.3 × 10 ⁻² m / second ² ). While scooping with a scooping roller with a diameter of 50 mm.

  The specific method for obtaining the melt tension of the polyolefin resin is to measure the melt tension of the string-like material detected with a detector that performs scooping at a scooping speed of 500 (rpm) and is connected to a tension detecting pulley over time. When the measurement is made and shown in a chart with MT (mN) on the vertical axis and time (seconds) on the horizontal axis, a graph with amplitude is obtained. Next, the median value (X) of the amplitude of the portion where the amplitude is stable is taken. In the present invention, this value (X) is the melt tension. In the measurement, a specific amplitude that occurs infrequently is ignored.

  However, when the string-like object hung on the pulley for tension detection is cut up to a scissor cutting speed of 100 (rpm), a scooping speed R (rpm) when the string-like object is cut is obtained. Next, the median value (X) of the amplitude is adopted as the melt tension from the graph obtained in the same manner as described above at a constant scraping speed of R × 0.7 (rpm).

  When the polyolefin resin is a polypropylene resin, measurement is performed in the same manner as in the case of the polyethylene resin except that the resin temperature is 230 ° C., and the string-like material hung on the tension detection pulley is cut up to a scooping speed of 500 (rpm). When it does, the barbing speed | rate R (rpm) when a string-like thing cut | disconnects is calculated | required. Next, the median value (X) of the amplitude is adopted as the melt tension from the graph obtained in the same manner as described above at a constant scraping speed of R × 0.7 (rpm).

  In the present invention, within a range that does not impede its purpose and effect, a polyolefin resin is a styrene resin such as polystyrene, an elastomer such as ethylene propylene rubber, a butene resin such as polybutene, and a vinyl chloride resin such as polyvinyl chloride. 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. The lower limit is approximately 0.01% by weight.

  Various additives may be added to the polyolefin resin. Examples of various additives include colorants, nucleating agents, antioxidants, heat stabilizers, weathering agents, ultraviolet absorbers, flame retardants, inorganic fillers, antibacterial agents, and shrinkage inhibitors. In this case, the amount added is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 3% by weight or less. The lower limit is approximately 0.01% by weight.

Next, the polymer type antistatic agent preferably used in the present invention will be described in detail.
The number average molecular weight of the polymer type antistatic agent in the present invention is preferably 2000 or more, more preferably 2000 to 100,000, still more preferably 5000 to 60000, and particularly preferably 8000 to 40000, and is composed of a surfactant. A distinction is made from inhibitors. The upper limit of the number average molecular weight of the polymer type antistatic agent is approximately 1,000,000. By setting the number average molecular weight of the polymer type antistatic agent within the above range, the antistatic performance is more stably expressed without being influenced by the environment, and the antistatic agent migrates to the packaged body surface. There is no pollution.

  In addition, the said number average molecular weight is calculated | required using high temperature gel permeation chromatography. For example, when the polymer antistatic agent is a polyether ester amide or a hydrophilic resin mainly composed of polyether, the sample concentration is 3 mg / ml using orthodichlorobenzene as a solvent, and the column temperature is 135 ° C. using polystyrene as a reference substance. It is a value measured under the conditions. In addition, the kind of said solvent and column temperature are suitably changed according to the kind of polymeric antistatic agent.

  The block of the polyolefin (a) of the block polymer (A) used as the polymer type antistatic agent includes a carbonyl group (preferably a carboxyl group. In addition, as a preferable embodiment of all the carbonyl groups exemplified below, A polyolefin having a hydroxyl group at both ends of the polymer (a2), and a polyolefin having a hydroxyl group at both ends of the polymer (a3). Further, polyolefin (a4) having a carbonyl group at one end of the polymer, polyolefin (a5) having a hydroxyl group at one end of the polymer, and polyolefin (a6) having an amino group at one end of the polymer can be used. Of these, polyolefins (a1) and (a4) having a carbonyl group are preferable because of easy modification.

  As the block of the hydrophilic polymer (b) constituting the block polymer (A), polyether (b1), polyether-containing hydrophilic polymer (b2), cationic polymer (b3) and anionic polymer (b4) are used. it can. As (b1), polyether diol (b1-1), polyether diamine (b1-2), and modified products thereof (b1-3) can be used. (b2) includes polyether ester amide (b2-1) having a segment of polyether diol (b1-1) as a polyether segment forming component, and polyether amide imide (b2) having the same segment (b1-1) -2), polyether ester (b2-3) having the same segment (b1-1), polyether amide (b2-4) having the same segment (b1-2) and (b1-1) or ( Polyether urethane (b2-5) having the segment b1-2) can be used. As (b3), a cationic polymer having 2 to 80, preferably 3 to 60, cationic groups (c2) separated by a nonionic molecular chain (c1) in the molecule can be used. (b4) includes dicarboxylic acid (e1) having a sulfonyl group and diol (b0) or polyether (b1) as essential structural units, and 2 to 80, preferably 3 to 60 in the molecule. An anionic polymer having a sulfonyl group can be used.

  Specific examples of the block polymer (A) include the following block polymers (A1) to (A4).

[Block polymer (A1)]
The block polymer (A1) has a structure in which the blocks (a1) and (b1) are alternately and repeatedly bonded, and includes a polymer having a repeating unit represented by the general formula (1) in Table 1 below. In general formula (1), n is an integer of 2 to 50, ^one of R ¹ and R ² is a hydrogen atom, the other is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, y is an integer of 15 to 800, E ¹ is a residue obtained by removing a hydroxyl group from a diol (b0), A ¹ is an alkylene group having 2 to 4 carbon atoms, m and m ′ are integers of 1 to 300, and X and X ′ are general formulas shown in Table 1 below. (2) to a group selected from the groups represented by (8) and a group selected from the corresponding groups represented by (2 ′) to (8 ′), that is, X is a group represented by the general formula (2) In this case, X ′ is a group represented by the general formula (2 ′), and the same relationship applies to the general formulas (3) to (8) and (3 ′) to (8 ′).

In general formulas (2) to (8) and (2 ′) to (8 ′) in Table 1, R ³ and R ³ ′ are trivalent hydrocarbon groups having 2 to 3 carbon atoms, and R ⁴ is 1 carbon atom. ˜11 divalent hydrocarbon group, R ⁵ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ⁶ is a hydrocarbon group having 2 to 22 carbon atoms, E ² represents an organic diisocyanate residue, r is 1 to 10, u and v are 0 or 1. Q, Q ′, T and T ′ are groups shown in Table 2 below.

ただし、Ｒ^５は水素原子又は炭素数１〜１０のアルキル基、Ｒ^７は水素原子又はメチル基、tはＲ^７がメチル基のとき０、水素原子のとき１である。一般式(１)で示される繰り返し単位中の｛ ｝内のポリエーテルセグメント｛(ＯＡ^１)ｍ-Ｏ-Ｅ^１-Ｏ-(Ａ^１Ｏ)ｍ’｝は、前記ポリエーテル(ｂ１)のポリエーテル部分により構成され、式中のＥ^１，Ａ^１、ｍ及びｍ’は前記と同様である。一般式(１)におけるＥ^１は、脂肪族二価アルコール、二価フェノール又は三級アミノ基含有ジオールから水酸基を除いた残基であることが好ましい。

However, R ⁵ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ⁷ is a hydrogen atom or a methyl group, t is 0 when R ⁷ is a methyl group, a 1 when hydrogen atoms. The polyether segment {(OA ¹ ) m—O—E ¹ —O— (A ¹ O) m ′} in {} in the repeating unit represented by the general formula (1) is the same as that of the polyether (b1). Consists of a polyether moiety, and E ¹ , A ¹ , m and m ′ in the formula are the same as described above. E ¹ in the general formula (1) is preferably a residue obtained by removing a hydroxyl group from an aliphatic dihydric alcohol, a dihydric phenol or a tertiary amino group-containing diol.

In the general formula (1), the block polymer (A1) in which X is a group represented by the general formula (2) and X ′ is a group represented by the general formula (2 ′) is a polyolefin (a1 ) And polyether diol (b1-1) can be directly reacted. R ³ and R ³ ′ in the general formulas (2) and (2 ′) are shown in [Table 3]. (R ⁴ is a hydrogen atom or a methyl group, t is 1 when R ⁴ is a hydrogen atom, and 0 when R ⁴ is a methyl group.) For example, for carbonyl modification of polyolefin, maleic acid or When fumaric acid is used, R ³ is —CH ₂ —CH <and R ³ ′ is> CH—CH ₂ —.

  The amount of the polyether (b1) constituting the block polymer (A1) is usually 20 to 90% by weight, preferably 25 to 90% by weight, particularly preferably based on the total weight of (a1) and (b1). 30 to 70% by weight. Mn of (A1) is usually 2000 to 60000, preferably 5000 to 40000, particularly preferably 8000 to 30000.

  In the structure of the block polymer (A1), the average repeating number (Nn) of the repeating units of the polyolefin (a) block and the hydrophilic polymer (b) block is usually 2 to 50, preferably 2.3 to 30. More preferably, it is 2.7 to 20, particularly preferably 3 to 10.

[Block polymer (A2)]
The block polymer (A2) comprises a polyolefin (a) block and a hydrophilic polymer (b) block bonded in the (a)-(b) type or (a)-(b)-(a) type. Block polymer. (A2) can be obtained by reacting (b2) with a polyolefin (a4) having a carbonyl group represented by any one of the general formulas (9) to (11) in Table 4 at one end of the polymer.

In the formula, R ⁸ is a polyolefin residue, Q ′ is a group represented by the formula —CH (R ¹⁰ ) —CH═C (R ¹⁰ ) —CH ₂ —, and R ⁹ is a trivalent carbon atom having 2 to 3 carbon atoms. A hydrogen group, R ¹⁰ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ¹¹ is a hydrogen atom or a methyl group. As (b2), those represented by the general formula (19) are preferable. In the formula (19), E ³ is a polyether group-containing hydrophilic polymer residue, R ¹² and R ¹³ are hydrogen atoms, the formula —CO—NH—E ² —NHCOO—R ¹⁴ —NH ₂ , the formula —CO—NH -E ² -NCO, group represented by formula -G or formula -CH ₂ CH (OH) CH ₂ -O-E ⁴ -OG, P is 0 or 1, and A ² is alkylene having 2 to 4 carbon atoms Group or a group represented by the formula — (R ¹⁵ —CO) r—, wherein R ¹⁵ includes a divalent hydrocarbon group having 1 to 11 carbon atoms (hereinafter referred to as a saturated hydrocarbon group or an unsaturated hydrocarbon group). ), R is an integer of 1 to 10, R ¹⁴ is a divalent hydrocarbon group having 2 to 12 carbon atoms, E ² is a residue of an organic diisocyanate, G is a glycidyl group, and E ⁴ is a diglycidyl ether (G—O). -E ⁴ -OG) represents a residue obtained by removing a glycidyloxy group. R ¹² and R ¹³ are preferably a hydrogen atom and / or a group represented by the formula —CO—NH—E ² —NCO. In general formula (19), E ³ is preferably a group represented by general formula (20). In general formula (20), E ⁵ is a residue of polyether (b1), D is an oxygen atom and / or imino group, Z is a polymer segment selected from the group consisting of polyesteramide, polyamideimide, polyester, polyamide and polyurethane And a segment represented by any one of the general formulas (21) to (27) is preferable. u is 0 or 1, and w is usually 2 to 50, preferably 3 to 30. Z is preferably a polyesteramide segment represented by the general formula (21). In general formulas (21) to (27), E ⁶ is a residue obtained by removing a carboxyl group from a dicarboxylic acid having 4 to 20 carbon atoms, and E ⁷ is a three carboxyl group from a trivalent or tetravalent aromatic carboxylic acid. E ⁸ is a residue from a polyamide-forming component selected from the group consisting of a monoamide of a dicarboxylic acid having 4 to 12 carbon atoms and a diamine having 2 to 12 carbon atoms and an aminocarboxylic acid having 6 to 12 carbon atoms. Residue excluding an amino group and a carboxyl group, E ⁹ is a polyester selected from the group consisting of an ester of a dicarboxylic acid having 4 to 12 carbon atoms and the diol (b0) described above and an oxycarboxylic acid having 6 to 12 carbon atoms. Residues excluding the terminal hydroxyl group and carboxyl group from the forming component, s, s ′, s ″ are 0 or an integer of 1 to 50, (s + s ′) is at least 1, A ³ is 2 to 4 carbon atoms alkylene group or the formula -R ¹ A group represented by ^{-CO-, R 16} is a divalent hydrocarbon group having 1 to 11 carbon atoms, q is 0 or an integer of from 1 to ^{10, E 10} is the formula ^{-CO-D-E 11 -D-} CO- A group represented by NH—E ² —NH—, E ² is a residue of an organic diisocyanate, D is an oxygen atom and / or imino group, and E ¹¹ is a residue of a chain extender. As (A2), one or both of the ends of (b2) were replaced with groups represented by the following general formulas (12) to (14) {when the end of (b2) is a hydroxyl group or an epoxy group} Having a structure (bonded via an ester bond); having a structure in which a group represented by the general formulas (15) to (17) {when the terminal of (b2) is an amino group or an isocyanate group} is substituted (an amide bond) And a group represented by the general formula (18) {when the terminal of (b2) is an amino group} (bonded via an imide bond).

The polyolefin residue R ⁸ has the formula R ¹⁷ — {CH (R ¹⁸ ) —CH (R ¹⁹ )} y— (wherein R ¹⁷ is a hydrogen atom or a group represented by H ₂ C═CH—, R ¹⁸ And one of R ¹⁹ is a hydrogen atom, the other is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and y is an integer of 15 to 800).

  The amount of (b2) constituting the block polymer (A2) is usually 20 to 80% by weight, preferably 30 to 70% by weight, based on the weight of (A2). Mn of (A2) is usually 2000 to 60000, preferably 5000 to 40000. In the structure of the block polymer (A2), the average repeating number (Nn) of the repeating units of the polyolefin (a) block and the hydrophilic polymer (b) block is usually 0.4 to 2.1, preferably 0. 0.5 to 2.0, more preferably 0.6 to 1.9, and particularly preferably 0.7 to 1.8.

[Block polymer (A3)]
The block polymer (A3) contains 2 to 80, preferably 3 to 60 cationic groups (c2) separated by a nonionic molecular chain (c1) in the molecule as the hydrophilic polymer (b). Having a block of the cationic polymer (b3) having a structure in which (a) and (b3) are repeatedly and alternately bonded. Mn of (A3) is usually 2000 to 60000, preferably 5000 to 40000, particularly preferably 8000 to 30000. The content of the cationic group (c2) in (A3) is 2 to 500, preferably 10 to 300, particularly preferably 15 to 250, per molecule of (A3). The Mn of (A3) per cationic group (c2) is usually 120 to 30000, preferably 200 to 6000, particularly preferably 300 to 4000.

  In the structure of the block polymer (A3), the average repeating number (Nn) of the repeating units of the polyolefin (a) block and the hydrophilic polymer (b) block is usually 2 to 50, preferably 2.3 to 30. More preferably, it is 2.7 to 20, particularly preferably 3 to 10.

[Block polymer (A4)]
The block polymer (A4) has, as (b), dicarboxylic acid (e1) having a sulfonyl group and diol (b0) or polyether (b1) as essential structural units, and preferably 2 to 80 in the molecule, Has a block of an anionic polymer (b4) having 3 to 60 sulfonyl groups, and has a structure in which (a) and (b4) are bonded alternately and repeatedly. Mn of (A4) is usually 2000 to 60000, preferably 5000 to 40000, particularly preferably 8000 to 30000. The content of the sulfonyl group in (A4) is 2 to 500, preferably 10 to 300, particularly preferably 15 to 250, per molecule of (A4). Mn of (A4) per sulfonyl group is usually 120 to 30000, preferably 200 to 6000, particularly preferably 300 to 4000.

  In the structure of the block polymer (A4), the average number of repeating units (Nn) of the repeating units of the polyolefin (a) block and the hydrophilic polymer (b) block is usually 2 to 50, preferably 2.3 to 30. More preferably, it is 2.7 to 20, particularly preferably 3 to 10.

  The melting point of the polymer antistatic agent is preferably 70 to 270 ° C., more preferably 80 to 230 ° C., and particularly preferably 80 to 200 ° C. from the viewpoint of antistatic function expression.

  The melting point of the polymer antistatic agent can be measured by a method based on the following JIS K7121 (1987). That is, pretreatment is performed under the condition (2) for condition adjustment of the test piece in JIS K7121 (1987) (however, the cooling rate is 10 ° C./min), and a melting peak is obtained by raising the temperature at 10 ° C./min. . The temperature at the top of the obtained melting peak is taken as the melting point. When two or more melting peaks appear, the temperature at the top of the melting peak having the largest area is defined as the melting point. However, when there are a plurality of melting peaks having the largest area, the melting point is the temperature at the apex of the melting peak on the highest temperature side among the melting peaks.

The polymer antistatic agents can be used alone or in combination.
The polymer antistatic agent as described above is commercially available, for example, under the trade names of “SD100” manufactured by Mitsui DuPont Polychemical Co., Ltd. and “Pelestat 300” manufactured by Sanyo Chemical Industries, Ltd.

In the foam of the present invention, the polymer type antistatic agent is contained in the foam in an amount of 8% by weight or less, the apparent density of the foam is 15 to 65 g / L, and the surface inherent property after ultrasonic cleaning with ethanol is used. The resistivity is 1 × 10 ⁸ to 1 × 10 ¹³ (Ω).
In order to obtain the said foam, the manufacturing method mentioned above is mentioned, for example. In the foam of the present invention, the above-described polymer antistatic agent is uniformly dispersed. Therefore, the foam has a permanent antistatic function, and exhibits excellent antistatic properties immediately after production without depending on the standing time or humidity conditions after production. Further, surface contamination such as stickiness or whitening of the surface of the packaged body hardly occurs. As the polymer type antistatic agent, those mentioned above are preferably mentioned.

  Examples of the shape of the foam in the present invention include a rod shape, a sheet shape, and a plate shape. Among these, a sheet shape or a plate shape is preferable from the viewpoint of easy packing of an article to be packaged as a packaging material and easy thermoforming.

In the foam of the present invention, the content of the polymer antistatic agent is 8% by weight or less and the apparent density is 15 to 65 g / L. When the apparent density is within this range, the polyolefin resin containing the polymer type antistatic agent is stretched at the time of foaming. Therefore, even if the content of the polymer type antistatic agent is 8% by weight or less, it exhibits excellent antistatic properties that the surface resistivity is 1 × 10 ⁸ to 1 × 10 ¹³ (Ω). Further, the possibility of causing surface contamination of the packaged body is extremely small.
If the content of the polymer antistatic agent exceeds 8% by weight, the bubble diameter is coarse and the appearance is deteriorated, and the closed cell ratio may be lowered. From the above viewpoint, the content of the polymer antistatic agent is preferably 7% by weight or less, and more preferably 6.5% by weight or less. On the other hand, the lower limit is preferably 2% by weight or more because there is a possibility that the antistatic property that the surface specific resistivity is 1 × 10 ⁸ to 1 × 10 ¹³ (Ω) may not be exhibited. 5% by weight or more is more preferable, and 4% by weight or more is particularly preferable.

  When the apparent density of the foam exceeds 65 g / L, there is a possibility that the antistatic property is deteriorated because the polyolefin-based resin containing the polymer type antistatic agent due to the growth of bubbles at the time of foaming does not have the effect of stretching. From this viewpoint, 61 g / L or less is preferable, 51 g / L or less is more preferable, and 44 g / L or less is more preferable. On the other hand, when the apparent density is less than 15 g / L, the foaming ratio is too large and the physical strength required for the packaging material may be reduced. From this viewpoint, 15 g / L or more is preferable, 18 g / L or more is more preferable, and 21 g / L or more is more preferable.

In the foam of the present invention, the surface resistivity after ultrasonic cleaning using ethanol is 1 × 10 ⁸ to 1 × 10 ¹³ (Ω).
When the surface resistivity exceeds 1.0 × 10 ¹³ (Ω), the antistatic property is insufficient, static charges accumulate on the surface of the foam, and dust tends to adhere. In order to make dust less likely to adhere, the surface resistivity is preferably 5 × 10 ¹² (Ω) or less, and more preferably 1 × 10 ¹² (Ω) or less.
On the other hand, when the surface resistivity of the foam is less than 1 × 10 ⁸ (Ω), the antistatic properties required for the packaging material may be excessive in quality, which may increase the cost.

  The foam of the present invention does not lose its antistatic effect even after ultrasonic cleaning with ethanol. On the other hand, when a surfactant-based antistatic agent such as monoglycerin ester is added to the foam, the antistatic effect is lost when ultrasonic cleaning is performed with ethanol. That is, when a surfactant type antistatic agent is used, the antistatic effect is exhibited by the antistatic agent bleeding out on the surface of the molded product and taking in moisture in the air. Therefore, even if the antistatic property is expressed in a normal state, the antistatic property is lost because the antistatic agent is washed away from the resin surface after ultrasonic cleaning with ethanol. Therefore, measuring the surface resistance after ultrasonic cleaning with ethanol is effective as a means for determining the persistence of the antistatic property of the resin layer.

  In this specification, “ultrasonic cleaning using ethanol” is performed by placing ethanol at 23 ° C. in a beaker and sinking a test piece (length 100 mm × width 100 mm × thickness: thickness of the test piece) cut out from the foam. After ultrasonic cleaning for 24 hours, the test piece is left to stand for 36 hours in an atmosphere of 30 ° C. and 30% relative humidity, and dried. The surface resistivity after ultrasonic cleaning with ethanol is measured in accordance with JIS K6911 (1979) after conditioning the test piece immediately after the ultrasonic cleaning operation.

In the foam of the present invention, the average cell size in the extrusion direction: X (mm), the average cell size in the width direction: Y (mm), and the average cell size in the thickness direction: Z (mm) are as follows. The relationship shown is established.
0.35 ≦ Z / X ≦ 1.2 (1)
0.35 ≦ Z / Y ≦ 1.2 (2)

  If the values of Z / X and Z / Y are in the ranges shown in the above formulas (1) and (2), the surface resistivity can be lowered even with a small amount of the polymer antistatic agent. The closer the value of 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. If the values of Z / Y and Z / Y are less than 0.35, the compression strength may be deteriorated. From this viewpoint, the range of Z / Y and Z / Y is preferably 0.4 or more, and more preferably 0.45 or more. On the other hand, when the values of Z / X and Z / Y exceed 1.2, uneven thickness called corrugation may occur and the appearance may deteriorate. From this viewpoint, the range of Z / Y and Z / Y is preferably 1.1 or less, and more preferably 1.0 or less.

In the foam of the present invention, the average cell diameter in the thickness direction: Z (mm) preferably satisfies the following relationship.
0.2 ≦ Z ≦ 1.4 (3)
When the value of Z is in the range indicated by the above formula (3), the foam has excellent surface smoothness and good appearance. If the value of Z is less than 0.2, the open cell ratio tends to be high, so that the rigidity such as compressive strength may be low. From this viewpoint, the range of Z is preferably 0.3 or more, and more preferably 0.4 or more. On the other hand, when it exceeds 1.4, uneven thickness called corrugation may occur and the appearance may be deteriorated. From this viewpoint, the range of Z is preferably 1.3 or less, and more preferably 1.2 or less.

When the foam of the present invention has a thickness of 1 to 2 mm, it is often used as a cushioning material for packaging. In that case, the ranges of the values of Z / X, Z / Y and Z are more preferably shown below.
0.5 ≦ Z / X ≦ 0.85 (7)
0.5 ≦ Z / Y ≦ 0.85 (8)
0.3 ≦ Z ≦ 0.6 (9)
When the values of Z / X, Z / Y, and Z are within the ranges indicated by the above formulas (7), (8), and (9), the foam has excellent appearance and buffering properties.

In the case of a thick sheet having a thickness of 3 mm or more according to the present invention, there are many cases involving secondary processing such as thermoforming or laminating a resin layer. In that case, the values shown below are more preferable for the values of Z / X, Z / Y and Z.
0.7 ≦ Z / X ≦ 1.05 (10)
0.7 ≦ Z / Y ≦ 1.05 (11)
0.6 ≦ Z ≦ 1.2 (12)
If the values of Z / X, Z / Y and Z are within the ranges shown by the above formulas (10), (11) and (12), the orientation of the foam is small and the restoring force to return to the original by heat is sufficient. Since it is small, cracks are less likely to occur in the foam when thermoforming, and secondary workability defects such as wrinkles on the laminated surface of the foam and the resin layer are less likely to occur when secondary processing is performed.

In this specification, the average bubble diameter in the extrusion direction, the average bubble diameter in the width direction, and the average bubble diameter in the thickness direction are respectively measured as follows.
Average cell diameter in the extrusion direction: The center part in the width direction of the foam is cut vertically 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: X (mm).
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: Y (mm).
Average cell diameter in the thickness direction: The center part in the width direction of the cut foam test piece was cut vertically along the extrusion direction, and a line segment was drawn in the vicinity of the central 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 average cell diameter can be adjusted by, for example, a method of decreasing the average cell diameter by increasing the pressure of the die or the amount of the cell regulator described above, although it depends on the polyolefin resin used.
The method for adjusting the Z / X and Z / Y bubble shapes depends on the polyethylene resin used. For example, when the bubbles are made flat in the extrusion direction, the value of Z / X is specifically 0. When .35 ≦ Z / X <1.0, it can be adjusted by a method such as decreasing the discharge amount or increasing the take-up speed. On the other hand, when the bubbles are almost spherical in the extrusion direction, specifically, when the value of Z / X is close to 1.0 or when it is 1.0 or more and 1.2 or less, the discharge amount is increased. It can be adjusted by reducing the speed.
When the bubbles are flat in the width direction, specifically, when the value of Z / Y is 0.35 ≦ Z / Y <1.0, the foam is extruded so as to spread in the width direction. When using an annular die, increase the ratio of the discharge diameter of the annular die to the diameter of the mandrel that is the cylindrical cooling device (the diameter of the mandrel that is the cylindrical cooling device / the discharge port diameter of the annular die). It can be adjusted by the method.
On the other hand, when the bubbles are spherical in the width direction, specifically, when the value of Z / Y is close to 1.0, or when the value is 1.0 or more and 1.2 or less, the foam expands in the width direction. In the case of using an annular die, it can be adjusted by a method of reducing the ratio between the discharge port diameter of the annular die and the diameter of the mandrel that is a cylindrical cooling device. Further, these methods can be combined and adjusted.

The foam of the present invention preferably has an open cell ratio of 65% or less.
When the open cell ratio is within this range, the cushioning properties for packaging applications are excellent even if the foam is thin. Furthermore, when thermoforming, it is excellent in mold reproducibility and can be molded into the same shape as the mold. From this viewpoint, the open cell ratio is preferably 60% or less, more preferably 50% or less, still more preferably 40% or less, and most preferably 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. Actual volume of test piece (sum of closed cell volume and resin part volume): a value calculated from Vx (L) by the following equation (13).

      S (%) = (Va−Vx) × 100 / (Va−W / ρ) (13)

However, Va, W, and ρ in the above equation (13) are as follows.
Va: apparent volume (L) calculated from the outer dimensions of the foam specimen used for measurement
W: Weight of foam test piece (g)
ρ: Density of resin constituting the foam test piece (g / L)

The density ρ (g / L) of the resin constituting the foam test piece and the weight W (g) of the foam test piece are the operations of cooling the foam after defoaming the foam with a hot press, It can be obtained from the obtained resin. The foam test piece must be stored in a non-compressed state in the sample cup attached to the air comparison hydrometer, so the test piece has an apparent volume of 25 mm and a width of 40 mm and an apparent volume of 0.025 L (25 cm ³ ). Minimize the number so that

  The melt tension at 190 ° C. of the polyolefin resin composition constituting the foam of the present invention is preferably 30 to 400 mN. If the melt tension is less than 30 mN, the foamability may be reduced, so that it may not be a lightweight foam, or may be a foam having poor thermoformability such as poor elongation when used in thermoforming applications. There is. Moreover, there exists a possibility that the external appearance of a foam may also become a bad thing. From this viewpoint, the melt tension of the polyethylene-based resin composition is more preferably 35 mN or more, and further preferably 40 mN or more. On the other hand, when the melt tension exceeds 400 mN, the open cell ratio is increased due to heat generation due to an increase in the die pressure during extrusion foaming, and the rigidity may be lowered. Moreover, there exists a possibility that thermoformability may fall. From this viewpoint, the melt tension is preferably 300 mN or less, and more preferably 250 mN or less.

  The melt tension at 190 ° C. of the polyethylene-based resin composition constituting the foam is to be used by defoaming a test piece cut from the foam, or by cutting the resin layer when the resin layer is laminated. It is measured in the same manner as described above except that it is used after degassing. The melt tension in the foam of the present invention is adjusted by using the polyethylene resin having the melt tension exemplified in the above-described method.

  The melt tension at 190 ° C. of the polypropylene resin composition constituting the foam of the present invention is preferably 30 to 400 mN. If the melt tension is less than 30 mN, the foamability may be reduced, so that it may not be a lightweight foam, or when used for thermoforming applications, the foam may have poor thermoformability such as poor elongation. There is. Moreover, there exists a possibility that the external appearance of a foam may also become a bad thing. From this viewpoint, the melt tension of the polyethylene-based resin composition is more preferably 35 mN or more, and further preferably 40 mN or more. On the other hand, when the melt tension exceeds 400 mN, the open cell ratio is increased due to heat generation due to an increase in the die pressure during extrusion foaming, and the rigidity may be lowered. Moreover, there exists a possibility that thermoformability may fall. From this viewpoint, the melt tension is preferably 300 mN or less, and more preferably 250 mN or less.

  The melt tension at 190 ° C of the polypropylene-based resin composition constituting the foam is that the test piece cut from the foam is used after defoaming, and the resin layer is cut off when the resin layer is laminated It is measured by the above-described method except that is defoamed and used.

The melt tension of the polyethylene resin composition constituting the foam of the present invention is measured using a test piece obtained by defoaming the foam. Therefore, the adjustment method of melt tension is adjusted using what corresponds to the polyethylene-type resin composition which forms the foamed layer at the time of extruding a foam from an extruder. Specifically, when a polyethylene resin composition that has already been melt-kneaded using a twin screw extruder or kneader as a polyethylene resin composition is introduced into an extruder to produce a foam, the polyethylene resin to be added is used. The composition is measured in advance and adjusted. Also, when two or more kinds of resins are separately fed into an extruder as a polyethylene resin composition to produce a foam, or a melt-kneaded polyethylene resin composition and a cell regulator are separately put into an extruder. When producing foams by charging, the results were obtained using samples obtained by melt-kneading using a twin-screw extruder or kneader in advance under the melt-kneading conditions assumed after the introduction of these extruders. It will be adjusted based on the original.
In addition, a polypropylene resin resin composition is adjusted similarly to the above.

  The foam of the present invention has an antistatic effect without depending on atmospheric temperature such as humidity, and is suitable for cushioning materials, heat insulating materials for construction, food containers, etc. Since it does not contaminate the surface of the product, it is useful as a cushioning material for packaging.

Hereinafter, the present invention will be described in more detail based on examples.
In addition, as a bubble regulator used in Examples 1-4 and Comparative Examples 1-4, talc (trade name “High Filler # 12” manufactured by Matsumura Sangyo Co., Ltd.) is 11.8 wt. Part, a foam control agent master batch comprising 5.9 parts by weight of sodium citrate was used.

The following were used as polyolefin resin.
PE1: Low density polyethylene “F102” manufactured by Sumitomo Chemical Co., Ltd. (crystallization temperature 97.8 ° C. density: 922 g / LMFR: 0.3 g / 10 min)
PE2: Low density polyethylene “NUC8008” manufactured by Nihon Unicar Co., Ltd. (crystallization temperature: 93.5 ° C., density: 917 g / L, MFR: 4.5 g / 10 minutes)
PP1: Propylene-ethylene block copolymer “SD632” manufactured by Sun Allomer Co., Ltd. (crystallization temperature 128 ° C., density: 900 g / L, MFR: 3.2 g / 10 minutes)

As the polymer type antistatic agent, those shown below were used.
Polymer antistatic agent P1: polyether-polypropylene block copolymer “Pelestat 300” manufactured by Sanyo Chemical Industries, Ltd. (melting point: 136 ° C., number average molecular weight: 14000, density: 990 g / L)
Polymer antistatic agent P2: Ciba Specialty Chemicals Co., Ltd. (mixture of polyetheresteramide and polyamide) “IRGASTAT P18” (melting point 180 ° C., number average molecular weight 19000, density 1043 g / L)

Example 1
A tandem extruder comprising two extruders having a diameter of 90 mm and a diameter of 120 mm was used as an extruder for producing a foam, and an annular die having a diameter of 95 mm was attached to the outlet of the extruder.

  2 parts by weight of a bubble control agent masterbatch is blended with 100 parts by weight of PE1 (low density polyethylene) as a polyolefin resin, and a polymer antistatic agent as a polymer antistatic agent with respect to 100 parts by weight of low density polyethylene 6.4 parts by weight was added and supplied to the raw material inlet of an extruder having a diameter of 90 mm, followed by heating and kneading to obtain a resin melt adjusted to about 200 ° C. A mixed butane of 70% by weight normal butane and 30% by weight isobutane as a physical foaming agent is press-fitted into the resin melt so as to be 25% by weight with respect to 100 parts by weight of low density polyethylene, and then an extruder having a diameter of 90 mm. It is transported to an extruder with a diameter of 120 mm connected to the downstream side of the resin, cooled and adjusted to a resin temperature (foaming temperature) of 110 ° C. and a die pressure of 7 to 10 MPa (G) to melt the foamable resin. The foamable resin melt was extruded through the annular die to form a cylindrical foam. The extruded cylindrical foam was incised while being drawn along a cooled cylinder to obtain the desired foam.

Example 2
Foam in the same manner as in Example 1 except that PE2 (low density polyethylene) is used as the main component of the polyolefin resin, the mixed butane content is 27 wt%, and the resin temperature (foaming temperature) is adjusted to 108 ° C. Got.

Example 3
Example except that the blending amount of the physical foaming agent was 23 parts by weight, 4.7 parts by weight of P1 “Pelestat 300” was added as a polymer antistatic agent, and the resin temperature (foaming temperature) was adjusted to 111 ° C. A foam was obtained in the same manner as in 1.

Example 4
A foam was obtained in the same manner as in Example 1 except that PP1 shown in Table 1 was used, the amount of the physical foaming agent was 8 parts by weight, and the resin temperature (foaming temperature) was adjusted to 152 ° C.

Table 6 summarizes the types of polyolefin resins (main raw materials) in Examples 1 to 4, the melt viscosity at 190 ° C, the melt tension, the types of polymer antistatic agents, the melt viscosity at 190 ° C, and the crystallization temperature. Table 7 summarizes the addition amount of the polymer type antistatic agent, the injection amount of the foaming agent, the foaming temperature, the blow ratio, the take-up speed, the discharge amount, and the like.
The melt viscosity at a measurement temperature of 190 ° C. and a shear rate of 100 sec ⁻¹ (shown in the table as “melt viscosity at 190 ° C.”), melt tension, and polymer type antistatic agent for the polyolefin resins in Table 6 The melt viscosity at 190 ° C. and the crystallization temperature are measured by the measurement method described above and are values obtained using raw material pellets.

The content of the polymer antistatic agent in the obtained foam, the melt tension of the polyolefin resin (indicated as “PO resin melt tension” in the table), the apparent density, the thickness of the foam, and the open cell ratio Table 8 shows the evaluation of the surface resistivity (after ethanol washing), bubble shape, appearance and overall evaluation.
In addition, the melt tension of the polyolefin resin in Table 8 is a value obtained by using the non-foamed resin obtained by defoaming the foam, measured by the measurement method described above.

Comparative Example 1
17.6 parts by weight of the polymer antistatic agent “Pelestat 300” manufactured by Sanyo Chemical Co., Ltd. is added to 100 parts by weight of the low density polyethylene, and the blending amount of mixed butane is 25 weights with respect to 100 parts by weight of the low density polyethylene. The foam was obtained in the same manner as in Example 1 except that the resin temperature (foaming temperature) was adjusted to 108 ° C.

Comparative Example 2
The foam was prepared in the same manner as in Example 1 except that the amount of the physical foaming agent was 8 parts by weight, the resin temperature (foaming temperature) was 113 ° C., and the blow ratio and take-up speed were adjusted to the values shown in Table 7. Obtained.

Comparative Example 3
A foam was obtained in the same manner as in Example 1 except that 1.5 parts by weight of the polymer antistatic agent “Pelestat 300” was added and the resin temperature (foaming temperature) was adjusted to 111 ° C.

Comparative Example 4
Extrusion foaming was performed in the same manner as in Example 1 except that “IRGASTAT P18” manufactured by Ciba Specialty Chemicals Co., Ltd. was used as the polymer antistatic agent. However, a crystallized product was generated immediately after extrusion, and only a foam having a surface irregularity was obtained, and the foam was not capable of measuring the surface resistivity. Therefore, the surface resistivity was not measured. The crystallized product immediately after extrusion is considered to be due to “IRGASTAT P18”, a polymer type antistatic agent.

Types of polyolefin-based resins (main raw materials) in Comparative Examples 1 to 4, melt temperature at a measurement temperature of 190 ° C., shear rate of 100 sec ⁻¹ (indicated in the table as “melt viscosity at 190 ° C.”), melt tension Table 6 shows the type of polymer antistatic agent, melt viscosity at 190 ° C., and crystallization temperature. The amount of polymer antistatic agent added, the amount of physical foaming agent injected, the foaming temperature, the blow ratio, the take-off Table 7 shows the speed and discharge amount.

  The content of the polymer antistatic agent in the obtained foam, the melt tension of the polyolefin resin (indicated as “PO resin melt tension” in the table), the apparent density, the thickness of the foam, and the open cell ratio Table 8 shows the evaluation of the surface resistivity (after ethanol washing), bubble shape, appearance and overall evaluation.

  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. As the conditions for adjusting the bubble shape, the foaming temperature (° C.), discharge rate (kg / hr), the ratio of the discharge diameter of the annular die to the diameter of the mandrel that is a cylindrical cooling device (in the table, the blow ratio And take-off speed (m / min) are shown in Table 1. The foaming temperature refers to the die temperature of the annular die whose oil temperature is controlled.

  The crystallization temperature of the polymer antistatic agent shown in Table 6 was determined by the measurement method described above.

The measurement of the content of the polymer antistatic agent in the foam, the apparent density, the open cell ratio, the surface specific resistivity (after ethanol washing), the appearance and the overall evaluation were performed as follows.
Note that the bubble shape was measured by the measurement method described above.

<Content of polymer antistatic agent>
When manufacturing a foam, it calculated | required from the addition amount of the polymer antistatic agent.

<Measurement of surface resistivity>
A test piece (length 100 mm × width 100 mm × thickness: test piece thickness) cut out from the foam was used as a sample.
In accordance with the method of JIS K6911 (1979) described above, the surface resistivity after 1 minute was applied after application at an applied voltage of 500 V, and the surface resistivity was determined from the average value of the measured values. As a measuring apparatus, “TR8601” manufactured by Takeda Riken Kogyo Co., Ltd. was used.
The surface resistivity after the ethanol washing in the table was measured after measuring the untreated surface resistivity, adjusting the state of the test piece as shown below, and immediately measuring the surface resistance under an environment of 23 ° C. and 50% RH. At that time, in accordance with the method of JIS K6911 (1979) described above, the surface resistance value after 1 minute was applied after application at an applied voltage of 500 V, and the surface resistivity was obtained from the average value of the obtained measured values. . As a measuring apparatus, “TR8601” manufactured by Takeda Riken Kogyo Co., Ltd. was used.

[Test specimen condition adjustment]
Branson's “BRANSONIC 220” was used as an ultrasonic cleaning device. First, 500 ml of ethanol was weighed in a 500 ml beaker, and the ethanol temperature was maintained at 23 ° C. Next, the test piece was immersed in ethanol having a purity of 99.5 Vol% or more by submerging it in a beaker using a wire mesh. Thereafter, the beaker with the test piece submerged is covered with a foil, and the beaker is placed in the concave storage portion of the ultrasonic cleaning apparatus containing 1.7 liters of water at 23 ° C. The apparatus was turned on and cleaning was started. After 8 hours from the start of washing, and further after 16 hours from the start of washing, an operation of adding ethanol at 23 ° C. was performed so that ethanol in the beaker became 500 ml. This additional operation of ethanol is an operation of replenishing ethanol because it is volatilized by ultrasonic cleaning and is reduced from the amount originally present in the beaker. After 24 hours from the start of cleaning, the ultrasonic cleaning apparatus was stopped, the test piece was taken out from the beaker, and immediately the test piece was left to stand for 36 hours in an atmosphere with a relative humidity of 30% and a temperature of 30 ° C. The condition adjustment of the test piece was completed.

<Appearance evaluation>
The appearance of the obtained foam was visually evaluated based on the following evaluation criteria.
○: The shape of the bubbles is uniform throughout, the bubble size is fine, and the surface smoothness is excellent.
(Triangle | delta): Although the shape of a bubble is uniform on the whole and is a fine bubble diameter, a few huge bubbles are seen in some places, and an unevenness | corrugation is seen partially.
X: Giant bubbles are seen, and the whole surface is uneven with the surface burned.

<Comprehensive evaluation>
Comprehensive evaluation was performed according to the following evaluation criteria based on evaluation of open cell ratio, surface resistivity, and appearance.
◎: There is one or more ◎, and the remainder is ○ ○: All are ○ ×: There is one or more ×

The open cell ratio was determined according to the following evaluation criteria.
A: The open cell ratio is 40% or less. O: The open cell ratio exceeds 40% and is 70% or less.
×: Open cell ratio is over 70%

The surface resistivity was measured according to the following evaluation criteria.
A: 1.0 × 10 ^{8 to} 1.0 × 10 ¹⁰ (Ω)
○: exceeding 1.0 × 10 ¹⁰ (Ω) to 1.0 × 10 ¹³ or less ×: exceeding 1.0 × 10 ¹³ (Ω)

  The values obtained by the methods described above were adopted for the measurement of the apparent density and the open cell ratio.

It is explanatory drawing which shows an example of the manufacturing method of this invention foam.

Explanation of symbols

11 Extruder 12 Die I Polyolefin Resin
II Polymer antistatic agent
III Physical blowing agent
IV Expandable polyolefin resin fat melt V Foam

Claims (5)

Extruded polymer antistatic agent having a crystallization temperature of 110 ° C. or less, a measurement temperature of 190 ° C., and a melt viscosity of 80 to 1000 Pa · s at a shear rate of 100 sec ⁻¹ , a polyolefin resin and a physical foaming agent A production method for obtaining a polyolefin resin foam by kneading in a machine to form a foamable polyolefin resin melt and extruding and foaming the foamable polyolefin resin melt. A polyolefin resin foam characterized by adding 2 to 8 parts by weight of an antistatic agent to 100 parts by weight of a polyolefin resin and extrusion-foaming so that the apparent density of the foam is 65 g / L or less. Production method.   The method for producing a polyolefin resin foam according to claim 1, wherein the polyolefin resin is a polyethylene resin having a melt tension at 190 ° C of 30 to 400 mN.   The method for producing a polyolefin resin foam according to claim 1, wherein the polyolefin resin is a polypropylene resin having a melt tension of 30 to 400 mN at 230 ° C. It contains 8% by weight or less of a polymeric antistatic agent, has an apparent density of 15 to 65 g / L, and has a surface resistivity of 1 × 10 ⁸ to 1 × 10 ¹³ (after ultrasonic cleaning with ethanol). Ω), and an average cell diameter satisfies the following formulas (1), (2) and (3): a polyolefin-based resin foam.
0.35 ≦ Z / X ≦ 1.2 (1)
0.35 ≦ Z / Y ≦ 1.2 (2)
0.2 ≦ Z ≦ 1.4 (3)
(However, X, Y, and Z are 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).)   The polyolefin resin foam according to claim 4, wherein the open cell ratio of the foam is 65% or less.

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