JP2004339498A - Polypropylene-based resin composition foamed sheet and multi-layer foamed sheet given by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polypropylene-based resin foamed sheet obtainable by using general-purpose polypropylene as a part of its base resin and having low density, a high closed-cell percentage, enough repressed drawdown, and good thermoformability. <P>SOLUTION: This foamed sheet is obtained by using a resin composition composed of a polypropylene-based resin (resin a) which has a zero-shear viscosity of 1×10<SP>5</SP>to 5×10<SP>5</SP>Pa/sec at 210°C in an amount of 5-99 wt% and a polypropylene-based resin (resin b) which has a zero-shear viscosity of 0.01×10<SP>5</SP>to 0.8×10<SP>5</SP>Pa/sec at 210°C and a melt flow rate of 0.5-20 g/10 min in an amount of 95-1 wt% as a base resin, wherein the foamed sheet has a density of 90-600 kg/m<SP>3</SP>. A multi-layer sheet is obtained by forming a non-foamed layer which contains a polypropylene-based resin as a main component on at least one of surfaces of the foamed sheet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a foamed sheet of a polypropylene-based resin composition and a multi-layered foamed sheet which can be provided at low cost with improved thermoformability.

  Conventionally, a polypropylene resin (hereinafter, referred to as high melt tension polypropylene) having a high melt tension (also referred to as a high melt tension) is used as a base resin of a foamed polypropylene resin sheet, and has a closed cell structure, and It is known that a foamable sheet that can be formed by thermoforming can be obtained (for example, see Patent Document 1).

  Patent Literature 1 discloses an extruded foam from a propylene-based resin exhibiting a specific melt tension and a specific half-crystallization time. Further, in the examples in the patent document, a foam sheet is disclosed in which the propylene-based resin exhibiting the specific melt tension and the specific half-crystallization time is used and the open cell portion is substantially eliminated. . Further, it is described that a dish-shaped container having a shape faithful to a mold can be obtained by plug-assist vacuum forming of the foamed sheet (one of the methods included in thermoforming).

  However, the high melt tension polypropylene is expensive because it requires special equipment for production and requires a separate process for increasing the melt tension. In recent years, there has been proposed a method of obtaining a foamed polypropylene resin sheet at a lower cost by using general-purpose polypropylene as a part of the base resin (for example, see Patent Documents 2 and 3).

  Patent Literature 2 discloses that a melt tension is 6 to 40 g, and a polypropylene resin having a free terminal long-chain branching is 10 to 50% by weight (hereinafter, referred to as%), and a melt tension is 0.01 g to less than 1 g. Further, an extruded polypropylene resin foam using a resin composition composed of 90 to 50% of a polypropylene resin having a ratio of a weight average molecular weight to a number average molecular weight of 3 to 8 as a base resin is disclosed. I have.

Specifically, the melt tension is 6 to 40 g, and is obtained by using a composition of a high melt tension polypropylene manufactured by Montel SDK Sunrise Co., Ltd., which is a polypropylene resin having a free terminal long chain branch, and a specific general-purpose polypropylene. A foam sheet having a closed cell structure with a density of about 250 to 350 kg / m ³ is disclosed, and it is described that thermoformability expressed as secondary moldability is also good.

  However, foams having a density range as disclosed herein are not sufficiently satisfactory in terms of their heat insulating properties and light weight, and further reduction in density is required.

  If a low density foamed sheet is to be obtained by employing the configuration of the base resin disclosed in Patent Document 2, there is a problem that the closed cell ratio is reduced. This is considered to be because, when trying to lower the density, the cell membrane in the foamed sheet is more strongly stretched and thinned, so that the cell membrane breaks without being able to withstand the growth of bubbles. In order to prevent this, it is necessary to increase the proportion of expensive high melt tension polypropylene so that the cell membrane can withstand stretching, and one of the effects of the document of obtaining a foamed sheet at low cost is greatly reduced. Would.

  Further, the foamed sheet disclosed in Patent Document 2 is not sufficiently satisfactory in thermoformability, and particularly has a problem that drawdown tends to be large. Drawdown refers to the amount of sagging of the foamed sheet when the foamed sheet is heated in the molding machine, and it is required that the drawdown be kept small even when the sheet is sufficiently heated. As a specific problem in the thermoforming of a foam sheet with a large drawdown, the heated foam sheet comes into contact with the lower heater and cannot be formed, or a part of the foam sheet is double drawn into the mold. It is likely that molding defects such as double-out occur, or that a part of the molded product becomes thinner at the stage of shaping after heating. For this reason, when thermoforming a foam sheet in which drawdown tends to be large, it is necessary to finely adjust the heating conditions.

  Patent Document 3 discloses that a base resin is a mixture of 15 to 70% of a polypropylene resin having a melt tension of 10 cN or more at 230 ° C. and 85 to 30% of a polypropylene resin having a melt tension of 5 cN or less at 230 ° C. A polypropylene-based resin extruded foam sheet having a specific density and a specific closed cell rate is disclosed.

Specifically, as a polypropylene resin having a melt tension at 230 ° C. of 10 cN or more, a high-melt tension polypropylene manufactured by Montel Canada (the same as the high-melt tension polypropylene manufactured by Montell SDK Sunrise) and a specific general-purpose polypropylene are used. A foamed sheet having a closed cell structure with a density of about 180 to 320 kg / m ³ obtained by using the composition is disclosed, and the foamed sheet is formed by a plug assist vacuum forming method (one of the methods included in the thermoforming method). It is described that the molded article can be molded into a better molded article.

  However, the configuration of the base resin disclosed in Patent Document 3 does not overcome the problem of trying to obtain a low-density foamed sheet, and the foamed sheet disclosed in Patent Document 3 However, the drawdown was not sufficiently suppressed.

  On the other hand, there has been disclosed a modified polypropylene resin having specific elongational viscosity characteristics, which is obtained by melt-kneading a polypropylene resin, an aromatic vinyl monomer and a radical polymerization initiator (for example, see Patent Document 4).

  Further, a modified polypropylene resin obtained by melt-kneading a polypropylene-based resin, an isoprene monomer, and a radical polymerization initiator is disclosed (for example, see Patent Document 5).

  Furthermore, a modified polypropylene resin obtained by melt-kneading a polypropylene-based resin, a 1,3-butadiene monomer and a radical polymerization initiator is disclosed (for example, see Patent Document 6).

  Patent Documents 4 to 6 disclose that the modified polypropylene resin disclosed in the documents is excellent in foam moldability.

  Further, a foamed sheet comprising a modified polypropylene-based resin composition obtained by melt-kneading a polypropylene-based resin, an isoprene monomer, and a radical polymerization initiator is disclosed (for example, see Patent Document 7).

  An example in Patent Document 7 discloses a foamed sheet having a high closed cell rate, which is made of the modified polypropylene resin composition.

  Further, it is described that a good molded product can be obtained from the foamed sheet by a plug molding method (one of the methods included in the thermoforming method).

  Further, a modified polypropylene resin having a specific equilibrium compliance Jeo and a specific zero shear viscosity ηo obtained by melt-kneading a polypropylene resin, a radical polymerizable monomer, and a radical polymerization initiator is extruded and foamed. The resulting foamed sheet having a specific density and a closed cell rate is disclosed (for example, see Patent Document 8).

  However, the foamed sheets disclosed in Patent Literature 7 and Patent Literature 8 also require one step for obtaining a modified polypropylene resin composition, and from the viewpoint of inexpensively obtaining a foamed polypropylene resin sheet. Is not enough.

  As described above, it has a low density, a high closed cell rate and a drawdown suppressed sufficiently small, has excellent heat insulating properties, lightweight properties, thermoformability, and there is no inexpensive polypropylene resin foam sheet at present. is there.

Japanese Patent No. 2859983 (pages 1 to 9) JP 2001-226510 A (pages 2 to 7) JP-A-2002-356573 (pages 2 to 9) JP-A-9-188728 (pages 2 to 11) JP-A-9-188729 (pages 2 to 9) JP-A-9-278836 (pages 2 to 9) JP-A-11-228726 (pages 2 to 7) JP 2001-139716 A (pages 2 to 9)

  The present invention has been made in order to reduce the problems of the prior art, and uses a general-purpose polypropylene as a part of the base resin, combining high closed cell ratio and good thermoformability even at low density. It is an object of the present invention to provide an inexpensive polypropylene-based resin foam sheet.

  The present inventors have conducted intensive studies in order to reduce the problems of the prior art, and as a result, a resin composition comprising a polypropylene resin having a specific zero-shear viscosity and another specific polypropylene resin has a foamed sheet. It has been found that when used as a base resin, the problems of the prior art can be reduced. Specifically, when a polypropylene resin showing a high zero-shear viscosity in a specific range is used as a part of the base resin, as a low-density foamed sheet, or even when the use ratio of general-purpose polypropylene is increased. It has been found that the drawdown can be suppressed to a sufficiently small level and a foamed polypropylene resin sheet exhibiting good thermoformability can be obtained, and the present invention has been completed.

That is, the present invention
5-99% of a polypropylene resin (resin a) having a zero-shear viscosity of 1 × 10 ^{5 to} 5 × 10 ⁵ Pa · sec at 210 ° C. and a zero-shear viscosity of 0.01 × 10 ^{5 to} 0.8 × at 210 ° C. 10 ⁵ Pa · sec, and a melt flow rate of a 0.5 to 20 g / 10 min of the polypropylene resin (resin b) ninety-five to one% of the resin composition the base resin consisting of a density 90~600kg / m ³ foam sheet (claim 1),
5% or more and less than 50% of a polypropylene-based resin (resin a) having a zero shear viscosity of 1 × 10 ^{5 to} 5 × 10 ⁵ Pa · sec at 210 ° C., and a zero shear viscosity of 0.01 × 10 ^{5 to} 0. A density of 90 is used as a base resin, which is a resin composition of 8 × 10 ⁵ Pa · sec and a melt flow rate of 0.5 to 20 g / 10 min, which is 95% or less and more than 50% of a polypropylene resin (resin b). Foam sheet of up to 600 kg / m ³ (Claim 2),
The foamed sheet according to claim 1, wherein the melt flow rate of the resin a is 0.01 g / 10 min or more and less than 0.3 g / 10 min (claim 3).
The foamed sheet according to claim 1, 2 or 3, wherein the density of the foamed sheet is 90 kg / m ³ or more and less than 150 kg / m ³ (Claim 4),
The foamed sheet according to claim 1, 2, 3 or 4, and the foamed sheet according to claim 1, 2, 3, 4 or 5 having a closed cell ratio of 60 to 99%. Multilayer foamed sheet having a non-foamed layer mainly composed of polypropylene resin (Claim 6)
About.

  According to the present invention, even when a general-purpose polypropylene is used as a part of the base resin, the polypropylene resin foam having a low density, a high closed cell ratio and a sufficiently low drawdown, and a good thermoformability. You can get a sheet.

The foamed sheet of the present invention has a zero shear viscosity at 210 ° C. of 1 × 10 ^{5 to} 5 × 10 ⁵ Pa · sec, more preferably 2 × 10 ^{5 to} 5 × 10 ⁵ Pa · sec, especially 2 × 10 ^{5 to} 3 The polypropylene-based resin (resin a) of × 10 ⁵ Pa · sec and the zero shear viscosity at 210 ° C. are 0.01 × 10 ^{5 to} 0.8 × 10 ⁵ Pa · sec, and more preferably 0.015 × 10 ^{5 to} 0. A resin composition comprising a polypropylene-based resin (resin b) at 5 × 10 ⁵ Pa · sec and a melt flow rate of 0.5 to 20 g / 10 min, and more preferably 2 to 15 g / 10 min, as a base resin I do.

The resin a is a component used for obtaining a foamed sheet having a small drawdown and exhibiting good thermoformability. When the resin a has a zero shear viscosity at 210 ° C. of less than 1 × 10 ⁵ Pa · sec, there is a tendency that good moldability, which is an effect of the present invention, is impaired. When the zero shear viscosity at 210 ° C. of the resin a exceeds 5 × 10 ⁵ Pa · sec, the resin temperature tends to increase in the melt processing step for obtaining the foamed sheet of the present invention.

  The zero shear viscosity is obtained by the following method.

  The sample resin was formed into a flat plate shape using a press machine adjusted to a temperature of 190 ° C., and punched out to a diameter of 25 mm with a punch to obtain a measurement sample.

  As a device, a rheometer SR-2000 manufactured by Rheometric Scientific FE is used.

  The measurement is performed at 210 ± 1 ° C. with a nitrogen gas flowing in the measurement system.

  In the measurement, the sample was sandwiched between parallel plates having a diameter of 25 mm, the gap between the two plates was adjusted to 1.4 ± 0.05 mm, the sample resin protruding from the plates was removed, and the sample was allowed to stand for 20 minutes. Apply stress for 300 seconds and record the creep compliance J (t) against time t.

  FIG. 1 shows an example of the measurement result.

  The zero shear viscosity is calculated as the reciprocal of the slope of a portion that can be regarded as a substantially straight line in the obtained curve indicating the relationship between J (t) and t. That is, the time is t (sec), the creep compliance is J (t) (/ Pa), and the time t and the increment of the creep compliance J (t) between two points on the portion that can be regarded as the straight line are Δt (sec). ) And ΔJ (t) (/ Pa), the zero shear viscosity is calculated as Δt / ΔJ (t) (Pa · sec).

  The melt flow rate of the resin a is preferably from 0.01 g / 10 min to less than 0.5 g / 10 min, and more preferably from 0.05 g / 10 min to less than 0.3 g / 10 min. When the melt flow rate of the resin a is less than 0.01 g / 10 minutes, the resin temperature tends to increase in the melt processing step for obtaining the foamed sheet of the present invention. When the content is 0.5 g / 10 minutes or more, good thermoformability, which is an effect of the present invention, tends to be impaired.

  In addition, the melt flow rate referred to in the present invention is a value measured at 230 ° C. and 2.16 kg according to a measurement method of JIS K7210.

  The method for obtaining the resin a as described above is not particularly limited. For example, as an example of a preferred embodiment, a polypropylene-based resin (hereinafter, also referred to as a raw material resin), a radical polymerizable monomer, and radical polymerization initiation And a method of melt-kneading the agent. Specifically, the methods described in Patent Documents 4, 5, and 6 can be suitably used as a method for obtaining resin a.

  When the resin (a) contains a monomer unit other than propylene and / or another resin or rubber, the propylene monomer unit contained in the resin (a) is preferably used in view of maintaining a high heat resistance characteristic of a polypropylene resin. It is preferably at least 75% of the total of a and resin b, more preferably at least 90% of the total.

  Specific examples of the resin a include, for example, a raw material selected from one or more of a homopolymer of polypropylene, a random copolymer of propylene and ethylene, a block copolymer of propylene and ethylene, and an ethylene-propylene rubber. Resin, radical polymerizable monomer selected from one or more of isoprene, styrene, 1,3-butadiene, ketone peroxide, peroxyketal, hydroperoside, dialkyl peroxide, diacyl peroxide Melt kneading with one or more radical polymerization initiators such as oxides, peroxydicarbonates and peroxyesters, which are so-called organic peroxides having hydrogen abstraction ability, at a temperature of 180 to 250 ° C. for 30 seconds to 60 minutes. And a modified resin obtained by the above method. At this time, although it depends on the conditions for melt-kneading, the amount of the radical polymerizable monomer is 0.02 to 10 parts and the amount of the radical polymerization initiator is 0.1 to 100 parts by weight (hereinafter, referred to as parts) of the raw material resin. It is preferable to adjust the resin to a range of 10 to 10 parts to obtain the resin a.

The resin b is a general-purpose polypropylene resin, and is a component used to reduce the cost and to manufacture a low-density foamed sheet by forming a mixture with the resin a. is there. Resin b is if zero shear viscosity at 210 ° C. of less than 0.01 × 10 ⁵ Pa · sec, there is a tendency that thermal moldability is poor because the drawdown becomes large, the 0.8 × 10 ⁵ Pa · sec If it exceeds, the resin temperature in the melt processing step tends to increase. When the melt flow rate of the resin b is less than 0.5 g / 10 minutes, the resin temperature tends to have to be increased in the melt processing step for obtaining the foamed sheet of the present invention. When the melt flow rate is more than 20 g / 10 minutes, the closed cell rate of the obtained foamed sheet of the present invention tends to be reduced.

  The resin b is a homopolymer of propylene, a copolymer of propylene with another monomer, or a mixture thereof with another resin or rubber. When the resin b contains a monomer other than propylene and / or another resin or rubber, the propylene monomer unit contained is the same as that of the resin a in that the high heat resistance characteristic of the polypropylene resin is maintained. It is preferably at least 75% of the total with the resin b, more preferably at least 90% of the total.

  Specific examples of the resin b include a homopolymer of propylene, a random copolymer of propylene and ethylene, and a block copolymer of propylene and ethylene. Of these, homopolymers of propylene are preferred because they are inexpensive. Specific examples of the other resin or rubber include ethylene-propylene rubber and polyethylene.

  The compounding ratio of the resin a and the resin b in the base resin is 5 to 99% of the resin a, more preferably 5% or more and less than 50%, particularly 10 to 40%, and 95 to 1% of the resin b and further 95% or less. It consists of more than 50%, especially 90-60%.

  When the compounding ratio of the resin a is less than 5%, good moldability, which is an effect of the present invention, tends to be impaired. When the compounding ratio of the resin a exceeds 99%, the cost reduction effect, which is the effect of the present invention, tends to be small. The cost increases as the amount of the resin a increases. When the amount of the resin a is less than 50%, and more preferably 40% or less, the gloss of the foamed sheet becomes good, and an inexpensive foamed sheet excellent in light weight, heat insulating property, thermoformability and gloss can be obtained.

  The foamed sheet of the present invention is obtained by a known extrusion foaming method using an extruder using a resin composition comprising a resin a and a resin b as a base resin. The physical form of the resin composition at this time is not particularly limited, and a preferable specific example is a blend of pelletized or powdered resin a and pelletized or powdered resin b. can give.

  As a specific example, after the resin composition is melted in an extruder at 130 to 300 ° C., and further at 150 to 280 ° C., a so-called physical foaming agent is injected, kneaded, cooled, and then extruded from a die. The method for obtaining a sheet is preferably used for producing the foamed sheet of the present invention.

  Examples of the physical foaming agent include aliphatic hydrocarbons such as propane, butane, pentane and hexane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, and dichlorodifluorocarbon. Methane, chloromethane, dichloromethane, chloroethane, dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, Halogenated hydrocarbons such as chloropentafluoroethane and perfluorocyclobutane; and inorganic gases such as water, carbon dioxide, and nitrogen. Or a combination of two or more, and the like. Above all, aliphatic hydrocarbons such as propane, butane, and pentane and carbon dioxide are preferable because they are inexpensive and have high solubility in a polypropylene resin.

  The amount of the physical foaming agent to be used may be adjusted according to the target density of the foamed sheet, and is usually in the range of 0.5 to 5 parts, and more preferably 1 to 4 parts based on 100 parts of the base resin. It is.

  At this time, a foam nucleating agent may be added to the base resin for the purpose of adjusting the cell diameter. Specific examples of the foaming nucleating agent preferably used include, for example, a mixture of sodium bicarbonate and an organic acid such as citric acid or a masterbatch thereof, talc, calcium carbonate or a masterbatch thereof.

  The amount of the foam nucleating agent to be used may be adjusted so as to obtain a required cell diameter within a range not impairing the effects of the present invention. The amount of the foaming nucleating agent is usually in the range of 0.01 to 5 parts, more preferably 0.02 to 3 parts, per 100 parts of the base resin.

  Further, as another example, a method for obtaining a foamed sheet by melt-kneading and cooling the resin composition and a powder or a masterbatch-formed chemical foaming agent in an extruder, and then extruding from a die is also described in the present invention. It is preferably used in the production of the foamed sheet of the invention.

  Examples of the chemical foaming agent include a mixture of an organic acid such as sodium bicarbonate and citric acid, an azo foaming agent such as azodicarbonamide and barium azodicarboxylate, N, N′-dinitrosopentamethylenetetramine, and N, N′-. Examples include nitroso-based blowing agents such as dimethyl-N, N'-dinitrosoterephthalamide, sulfohydrazide-based blowing agents such as p, p'-oxybisbenzenesulfonylhydrazide and p-toluenesulfonylsemicarbazide, and trihydrazinotriazine. .

  The amount of the powder or the master foamed chemical foaming agent used to obtain the foam sheet by the above method may be adjusted according to the density of the foam sheet to be produced. The amount of the chemical foaming agent is usually in the range of 0.5 to 200 parts, and more preferably 1 to 100 parts, per 100 parts of the base resin.

  Before obtaining the foamed sheet of the present invention, a rubber, an antioxidant, a metal deactivator, a phosphorus-based processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a metal soap may be added to the base resin in advance according to the purpose. Additives such as stabilizers, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants, antistatic agents, anti-shrinkage agents, as long as the effects of the present invention are not impaired. Is also good.

The density of the foamed sheet of the present invention produced in this manner is from 90 to 600 kg / m ³ , further from 90 to 250 kg / m ² , from the viewpoint of sufficient lightness and heat insulation, which are the effects of the present invention. It is particularly preferably 90 to 170 kg / m ³ , particularly preferably 90 kg / m ³ or more and less than 150 kg / m ³ . When the density is less than 90 kg / m ^3, thermoformability, which is an effect of the present invention, tends to be impaired. When the density exceeds 600 kg / m ³ , the effect of the present invention, that is, the effect of cost reduction, is impaired.

  The foam sheet of the present invention usually has a thickness of 0.5 to 5 mm. When the thickness is less than 0.5 mm or more than 5 mm, the thermoformability as an effect of the present invention tends to be impaired.

  Further, the foamed sheet of the present invention preferably has a closed cell rate of 60% or more, more preferably 65% or more. When the closed cell ratio is less than 60%, the thermoformability as an effect of the present invention tends to be impaired. Although the upper limit of the closed cell rate is 100%, it is usually preferably 99% from the viewpoint of easy production.

  Further, in the production of the foamed sheet of the present invention, according to the shape of the molded article to be obtained by thermoforming, the foamed sheet of the present invention is suitable for molding such that the foamed sheet can be easily stretched when heated or the foamed shape in the foamed sheet. For the purpose of adjustment, for example, by adjusting the take-up speed of the extruded foam sheet, the ratio of the diameter of the annular die to the diameter of the cooling cylinder (mandrel), or the like, the method of stretching the foam sheet at an appropriate ratio, A method in which temperature-controlled air is blown onto the surface of the foamed sheet thus formed can be preferably used.

  Further, the foamed sheet of the present invention may be a multilayer foamed sheet having a non-foamed layer mainly composed of a polypropylene resin on at least one surface.

  Specific examples of those preferably used as the polypropylene resin include propylene homopolymers, block copolymers of propylene and other monomers, random copolymers of propylene and other monomers or these. Mixtures.

  Preferred examples of the other monomer include ethylene, butene-1, and octene-1, and the content is preferably 0.5 to 20%.

  The term “main component” means that 80% or more of the component constituting the non-foamed layer is the polypropylene resin. Examples of the component other than the main component include polyethylene, ethylene-butene-1 copolymer, and ethylene. -Octene-1 copolymer and the like.

  The method for forming the non-foamed layer is not particularly limited, and a known method such as a heat laminating method or a binder laminating method can be used.

  Preferable specific examples include, for example, a method of fusing and integrating a film mainly composed of the above-mentioned polypropylene resin and a foamed sheet through a heated roll, and a film and a foamed sheet coated with an adhesive on a contact surface. Through a heated roll and press-bonding both via an adhesive, melting the resin composition containing the polypropylene-based resin as a main component in an extruder, and foaming the melt extruded from a die into a thin film. A method in which a non-foamed layer is formed by laminating on a sheet, and then pressure-bonded through a roll to form a multilayer foamed sheet. When laminating the melt on a foamed sheet, a film is further laminated to form a three-layer structure, and then a roll is formed. And a method of pressing to form a multilayer sheet.

  The thickness of the non-foamed layer is generally preferably about 10 to 250 μm, from the viewpoint that a multilayer foamed sheet can be easily obtained without impairing the thermoformability, which is an effect of the present invention.

  The foamed sheet or multilayer foamed sheet of the present invention can be formed into a molded article suitably used for various miscellaneous goods, various containers (cups, bowls, trays, etc.), automobile members, building materials, and the like by a known thermoforming method.

  Next, the present invention will be described in detail based on examples, but the present invention is not limited to such examples.

Production Examples 1 to 5
100 parts of raw material polypropylene (manufactured by Sumitomo Mitsui Polyolefin Co., Ltd., E102, melt flow index at 230 ° C., 2 g / 10 minutes) and t-butyl peroxy-isopropyl monocarbonate, a radical polymerization initiator (Nippon Oil & Fats Co., Ltd.) The mixture prepared by stirring and mixing 0.3 parts of Perbutyl I) with a ribbon blender is supplied to a twin-screw extruder (TEX44XCT-38, manufactured by Nippon Steel Works, Ltd.) with a measuring feeder, and a liquid pump is used. In the middle of the extruder, isoprene was supplied at a ratio of 2.5 parts to 100 parts of the raw material polypropylene, melt-kneaded in the twin-screw extruder, and melt-extruded to obtain a resin composition 1 (hereinafter referred to as resin). 1) was obtained.

  The twin-screw extruder was of the same-direction twin-screw type, had a screw diameter of 44 mmφ, and had a maximum effective screw length (L / D) of 38. The set temperature of the cylinder portion of this twin-screw extruder was 180 ° C. until the injection of isoprene monomer, 200 ° C. after the injection of isoprene, and the screw rotation speed was set at 150 rpm.

  Further, as shown in Table 1, the resin composition 2 (hereinafter referred to as “resin 2”) and the resin composition were prepared in the same manner as the resin 1 except that the type of the raw material polypropylene, the amount of the radical polymerization initiator, and the amount of isoprene were respectively changed. Pellets of a product 3 (hereinafter, referred to as a resin 3), a resin composition 4 (hereinafter, referred to as a resin 4), and a resin composition 5 (hereinafter, referred to as a resin 5) were obtained.

  Table 1 shows the zero-shear viscosities at 210 ° C. of the polypropylenes (homopolypropylene manufactured by Basell, PF-814, melt flow rate 3 g / 10 minutes) used in Comparative Examples as Resin 1 to Resin 5 and Resin 6.

  In Table 1, PL500A is a homopolypropylene manufactured by Sun Allomer Co., Ltd., melt flow rate 3.3 g / 10 min, B101WAT is a homopolypropylene manufactured by Sumitomo Mitsui Polyolefin Co., Ltd., melt flow rate 0.5 g / 10 min, J104W is Sumitomo Mitsui Homopolypropylene manufactured by Polyolefin Co., Ltd., melt flow rate: 5 g / 10 min, and PF-814 (resin 6): homopolypropylene manufactured by Basell, melt flow rate: 3 g / 10 min.

Example 1
30 parts of resin a as resin a and polypropylene as resin b (PL500A manufactured by Sun Allomer Co., Ltd., zero shear viscosity at 210 ° C. 0.08 × 10 ⁵ Pa · sec, melt flow rate 3.3 g / 10 min) (hereinafter referred to as resin 7), and 2 parts of a master batch of sodium bicarbonate-organic acid-based chemical blowing agent (PO510K, manufactured by Dainichi Seika Kogyo Co., Ltd.) in a ribbon blender with respect to 70 parts of resin a and resin b in total of 100 parts. Mixed.

  The obtained mixture was supplied to a tandem extruder having a first-stage cylinder diameter of 65 mm and a second-stage cylinder diameter of 90 mm, and was melted at 220 ° C. in the first-stage extruder. Further, 2.3 parts of isobutane as a foaming agent was press-fitted into 100 parts of the mixture at the tip of the extruder at the first stage, followed by melt-kneading, and then cooled to 160 ° C. to have a diameter of 68 mm and a gap between lip portions. After extruding from a 0.3 mm annular die, it was taken up by a mandrel having an outer diameter of 100 mmφ and wound up in a roll to obtain a foamed sheet.

  The thickness, density, closed cell rate, gloss, and drawdown of the obtained foamed sheet were measured by the following methods.

  Further, after the foamed sheet having an opening described later fixed to a clamp frame of 600 mm × 600 mm is heated for 60 seconds in a single-shot molding machine whose temperature is controlled as described later, a mold having an opening of 11 cm × 11 cm and a depth of 3.5 cm is used. Into a square tray to obtain a foam molded product.

  The obtained molded articles were classified according to the following criteria, and the moldability of the foam sheet was evaluated.

Next, hot water at 98 ° C. was poured into the molded article to a depth of 2.5 cm, and after 300 seconds, the temperature T ₁ of the hot water inside the molded article and the temperature T _{2 of the} external surface of the molded article were measured. The results were classified according to the following criteria, and the heat insulation of the molded article was evaluated.
Table 2 shows the results.

(thickness)
Ten thicknesses in the width direction were measured with calipers and averaged.

(density)
It was calculated from the weight and the volume determined by the submersion method.

(Closed cell rate)
The measurement was performed using a multi-pycnometer (manufactured by Yuasa Ionics Co., Ltd.) according to ASTM D-2856.

(Glossiness)
Using a gross checker (GLOS CHECKER IG-330, manufactured by Horiba, Ltd.) at 10 locations in the width direction, measurement was performed at a measurement angle of 60 degrees, and the average value was calculated.

(Drawdown)
From the obtained foamed sheet, a sample having a size of 635 mm × 635 mm was cut out, fixed to a clamp frame having an opening of 600 mm × 600 mm, and guided into a heating furnace of a molding machine in which heaters were vertically arranged. After heating for 100 seconds, the amount of sag at the center of the sample immediately after being drawn out of the heating furnace was measured and defined as the amount of drawdown.
The molding machine used was a VAS-66-45T single-shot molding machine manufactured by Senba System Co., Ltd., and the temperature was controlled at 180 ° C. by the heater directly above and below the sample, and the other heaters were equivalent to the center over the entire surface of the foam sheet. It was set to be the temperature.

(Moldability)
：: The thickness is uniform over the entire molded product, and no wrinkles due to double-out etc. are observed.
X: A part with uneven thickness and wrinkles are seen in a part of the molded product.

(Thermal insulation properties)
：: The value of T ₁ -T ₂ is 25 ° C. or more.
Δ: The value of T ₁ -T ₂ was 15 ° C. or more and less than 25 ° C.
×: The value of T ₁ -T ₂ is less than 15 ° C.

Examples 2 to 13 and Comparative Examples 1 to 11
As shown in Tables 2 and 3, a foamed sheet was obtained and evaluated in the same manner as in Example 1 except that the types and amounts of the resins a and b and the amount of the foaming agent were changed.
The results are shown in Tables 2 and 3.

Example 14
On one side of the foamed sheet obtained in Example 1, a 100 μm-thick unstretched polypropylene film (RXC-3, manufactured by Tocello Co., Ltd.) having a contact surface coated with a chlorinated polypropylene-based adhesive was applied at 200 ° C. Was pressed through a heated roll to obtain a multilayer foam sheet, and evaluated in the same manner as in Example 1.
Table 2 shows the results.

Example 15
On one side of the foamed sheet obtained in Example 7, a 100 μm-thick unstretched polypropylene film (RXC-3, manufactured by Tocello Co., Ltd.) having a contact surface coated with a chlorinated polypropylene-based adhesive was applied at 200 ° C. Was pressed through a heated roll to obtain a multilayer foam sheet, and evaluated in the same manner as in Example 1.
Table 2 shows the results.

  As is clear from Tables 2 and 3, the foamed sheet and the multilayered foamed sheet of the present invention have a high closed cell ratio even at a low density, a small drawdown, and excellent moldability.

  In addition, even if the usage ratio of the resin b, which is a general-purpose polypropylene, is increased while maintaining a low density, a high closed cell ratio and a small drawdown are maintained, and since good thermoformability is exhibited, the cost can be greatly reduced. It works. Also, the gloss becomes good. Furthermore, a molded article produced from the foamed sheet of the present invention having a low density can have excellent heat insulating properties.

It is an example of the graph which calculated | required the relationship between time t and creep compliance J (t) used for calculating zero shear viscosity of a polypropylene resin, and the reciprocal of the slope of the approximate straight line in the part which can be regarded as the straight line of this graph is It becomes zero shear viscosity.

Claims (6)

5-99% by weight of a polypropylene resin (resin a) having a zero shear viscosity at 210 ° C. of 1 × 10 ^{5 to} 5 × 10 ⁵ Pa · sec, and a zero shear viscosity at 210 ° C. of 0.01 × 10 ^{5 to} 0.8. in × 10 ⁵ Pa · sec, and a melt flow rate of a 0.5 to 20 g / 10 min of the polypropylene resin (resin b) ninety-five to one percent by weight of the resin composition the base resin consisting of a density 90 600 kg / m ³ foam sheet. 5% by weight or more and less than 50% by weight of a polypropylene resin (resin a) having a zero shear viscosity at 210 ° C. of 1 × 10 ^{5 to} 5 × 10 ⁵ Pa · sec, and a zero shear viscosity at 210 ° C. of 0.01 × 10 ⁵ to A resin composition consisting of a polypropylene resin (resin b) having a melt flow rate of 0.8 to 10 ⁵ Pa · sec and a melt flow rate of 0.5 to 20 g / 10 min. A foamed sheet having a density of 90 to 600 kg / m ³ . The foamed sheet according to claim 1, wherein the resin a has a melt flow rate of 0.01 g / 10 min or more and less than 0.3 g / 10 min. The foam sheet according to claim 1, 2 or 3, wherein the density of the foam sheet is 90 kg / m ³ or more and less than 150 kg / m ³ . The foamed sheet according to claim 1, wherein the closed cell rate is 60 to 99%. A multilayer foamed sheet comprising a foamed sheet according to claim 1, 2, 3 or 4 and a non-foamed layer mainly composed of a polypropylene resin formed on at least one surface.

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