JPWO2019112011A1 - Foam - Google Patents

Abstract

The foam of the present invention contains cellulose fibers and polypropylene, and the content of the cellulose fibers is in the range of 10% by mass or more and 65% by mass or less, and the density is 80 kg / m3 or less.

Description

The present invention relates to a foam containing cellulose fibers and polypropylene.
The present application claims priority based on Japanese Patent Application No. 2017-234423, Japanese Patent Application No. 2017-234424 and Japanese Patent Application No. 2017-234425 filed in Japan on December 6, 2017, and the contents thereof are described here. Invite.

The foam has excellent cushioning and heat insulating properties against physical impact, and is therefore used in various applications such as heat insulating materials, cushioning materials, and packaging materials. In recent years, a composition containing cellulose fibers and polypropylene has attracted attention as a material for foams.
For example, Patent Document 1 describes a foam obtained by supplying a paper component, a thermoplastic resin, and water to an extruder, heating and kneading the mixture in the extruder, and foaming with the vapor pressure of water. Further, in Patent Document 1, a crushed product obtained by crushing used paper with a crusher and having a side length of about 3 mm to 5 mm is used as a paper component, and a powdery polypropylene homopolymer is used as a thermoplastic resin. A foam of 0.085 g / cm ³ (85 kg / m ³ ) is described.

Japanese Unexamined Patent Publication No. 2000-273800

However, the conventional foam containing cellulose fibers does not have sufficient heat insulating properties when used as a heat insulating material, and is required to improve the heat insulating properties.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a foam containing cellulose fibers and having sufficient heat insulating properties when used as a heat insulating material.

The present invention employs the following configuration in order to solve the above problems.
[1] A foam containing cellulose fibers and polypropylene, wherein the content of the cellulose fibers is in the range of 10% by mass or more and 65% by mass or less, and the density is 80 kg / m ³ or less.
[2] The foam according to the above [1], which has a shape in which a plurality of granular foam particles are connected in a string shape or a strand shape.

[3] The foam according to the above [1], which comprises the cellulose fiber and the polypropylene and has a density of 70 kg / m ³ or less.

[4] Further, a resin additive is contained, and the resin additive is a vinyl resin, a polystyrene resin, a polyester resin, a polyamide resin, an acrylic resin, a polyether resin, a polyimide resin, an elastomer resin, It is at least one selected from the group consisting of sulfur-containing resins, phenol-based resins, and epoxy-based resins, and the content of the resin additive is in the range of 0.1% by mass or more and 30% by mass or less, and the polypropylene. The foam according to the above [1], which has a content of 5% by mass or more.
[5] The foam according to the above [4], which has a density of 70 kg / m ³ or less.

[6] Further, the polyurethane is contained, and the content of the polyurethane is in the range of 1% by mass or more and less than 20% by mass, and the content of the polypropylene is in the range of 15% by mass or more and 89% by mass or less. The foam according to [1].

According to the present invention, it is possible to provide a foam containing cellulose fibers and having sufficient heat insulating properties when used as a heat insulating material.

Hereinafter, embodiments of the foam of the present invention will be described.
The foam of the present embodiment contains cellulose fibers and polypropylene. The content of the cellulose fiber is in the range of 10% by mass or more and 65% by mass or less.

(Cellulose fiber)
As the material of the cellulose fiber contained in the foam of the present embodiment, one or 2 selected from wood-based fibers such as coniferous trees and hardwoods, non-wood-based fibers, ginseng fibers, and bacterial-derived fibers. More than a seed can be used. Specifically, for example, mechanical pulp (MP; mechanical pulp, GP; crushed wood pulp, RGP; refiner ground pulp, TMP; thermomechanical pulp, CTMP; chemithermomechanical pulp, etc.), chemical pulp (KP; craft) of the above materials. Pulp, SP; sulfide pulp, AP; alkaline pulp, etc.), recycled pulp (recycled paper such as used paper and scraps, cardboard) and the like can be used.

Examples of conifers used as materials for cellulose fibers include red pine, black pine, spruce, larch, larch, radiata pine, long leaf pine, short leaf pine, slash pine, loblory pine, white spruce, black spruce, fir, douglas. Examples include fur, balsam fur, spruce, and cypress. Examples of hardwoods include beech, oak, oak, eucalyptus, poplar and the like. Examples of non-wooden fibers include linter, cotton, rice straw, straw, oil palm empty fruit bunch (EFB), bamboo, sugar cane bagasse, hemp, cane, Manila hemp, flax, reeds and the like. Examples of gin skin fibers include mulberry and mitsumata. Examples of bacterial-derived fibers include bacterial cellulose and the like.

As the cellulose fiber contained in the foam of the present embodiment, it is preferable to use a defibrated and / or crushed paper, and it is preferable to use a defibrated waste paper. The method for defibrating paper is not particularly limited, and for example, a stone mill type grinder, a beating machine, a shredder, a cone crusher, a roll crusher, a cutter mill, a self-made crusher, a stamp mill, a mortar, and a mortar. , Roller mill, ring mill, jet mill, hammer mill, pin mill, rotary mill, vibration mill, planetary mill, bead mill, attritor and other crushers can be used. Examples of the crusher include a stone mill type crusher manufactured by Masuko Sangyo Co., Ltd. (trade name: Mascoroider), a beating machine manufactured by Aikawa Iron Works Co., Ltd. (trade name: RF single refiner), and a hand shredder manufactured by Sanwa Supply Co., Ltd. Product name: PSD-12) and the like.

As the cellulose fiber used as the material of the foam, it is preferable to use one having an average particle size of 10 μm to 5 mm, and more preferably 20 μm to 3 mm, as measured by the measuring method described later. When the average particle size of the cellulose fibers is 10 μm or more, the energy required for crushing is small, so that the burden on the environment is small and the manufacturing cost is low, which is preferable. When the average particle size of the cellulose fibers is 5 mm or less, high-magnification foaming is possible and a low-density foam is obtained, which is preferable.

"Measuring method of average particle size of cellulose fibers"
It means that the average particle size of the cellulose fibers used as the material of the foam in the present embodiment is a value measured by using Method 1 or Method 2 shown below. In this embodiment, method 1 or method 2 is used depending on the average particle size of the cellulose fibers. When the average particle size of the measured cellulose fibers is within the range of both method 1 and method 2, one or more of the two methods may be used.

(Method 1: Cellulose fibers having a particle size in the range of 0.01 μm to 3000 μm)
A dispersion liquid in which the cellulose fibers of the sample are dispersed in ion-exchanged water as a dispersion medium is prepared. Next, the dispersion liquid is irradiated with ultrasonic waves for 30 minutes in an ultrasonic bathtub as a pretreatment. Then, the particle size of the sample in the dispersion is measured using the measuring device shown below under the measuring conditions shown below.
The particle size is measured after the dispersion is placed in the cell of the measuring device and irradiated with ultrasonic waves for 1 minute in the measuring device. In addition, the dispersion medium is placed alone in the cell of the measuring device in advance, and the particle size is measured as a blank.
Each dispersion is measured twice to calculate an average value, which is used as the average particle size of the sample.

Measuring device: Laser diffraction / scattering type particle size distribution measuring device (manufactured by HORIBA, Ltd., trade name: LA-950V2)
Measurement conditions; Measurement unit: Wet
Measurement mode: Manual flow cell measurement
Particle size standard: Volume standard
Refractive index: 1.50-0.00i (sample refractive index) /1.33-0.00i (dispersion medium refractive index)

(Method 2: Cellulose fibers containing long fibers having a particle size of 3000 μm or more)
The cellulose fibers of the sample are uniformly dispersed on a paper surface having a length of 60 mm and a width of 80 mm, and images of arbitrary three places are taken. Next, the lengths of 100 or more cellulose fibers for each image are measured by a digital camera system for a microscope (made by GOKO Inter Co., Ltd., Macromax) and measurement software (manufactured by GOKO Inter Co., Ltd., GOKO Measure). The length of the cellulose fiber is measured along the shape of the fiber. However, in the case of a shape in which cellulose fibers are aggregated, the longest part is measured. The particle size distribution (histogram) is obtained with the length of the cellulose fibers measured in this way as the equivalent diameter of the circle, and the volume mean diameter (MV) is calculated. The volume mean diameter (MV) is calculated by the attached software (HORIBA NEXTGEN Project LA-950 for Windows Ver7.02) of the trade name: LA-950V2 manufactured by HORIBA, Ltd. The volume mean diameter (MV) is expressed by the following equation.
MV = Σ (vd) / Σv
(D in the equation indicates the interval representative value of the histogram of the particle size distribution, and v indicates the frequency of the volume (the volume of the sphere when the fiber length is the equivalent diameter of the circle) with respect to the entire particles included in each interval. The representative value indicates the square root of the product of the section lower limit value and the section upper limit value.)

The foam of the present embodiment has a cellulose fiber content in the range of 10% by mass or more and 65% by mass or less. When the content of the cellulose fibers is 10% by mass or more, a foam having a low density can be easily obtained. Further, when the content of the cellulose fiber is 65% by mass or less, the content of polypropylene can be sufficiently secured, and the strength of the foam is not insufficient.
The content of cellulose fiber and polypropylene in the foam can be regarded as the same as the ratio of the content of cellulose fiber and polypropylene used as the material of the foam.

(polypropylene)
As the polypropylene used as the material of the foam, for example, polypropylene having an MFR (melt flow rate, temperature: 230 ° C., load: 2.16 kg) in the range of 0.1 g / 10 minutes or more and 100 g / 10 minutes or less is used. It is preferable to use it. One type of polypropylene may be used alone, or two or more types of polypropylene having different characteristics such as MRF may be used in combination. For example, low MFR polypropylene having an MFR (temperature: 230 ° C., load: 2.16 kg) in the range of 0.1 g / 10 minutes or more and 20 g / 10 minutes or less, and MFR (temperature: 230) than the low MFR polypropylene. Two types of polypropylene having a high MFR of high ° C. and a load of 2.16 kg) may be used in combination. By using two or more types of polypropylene having different characteristics in combination, the density and thermal conductivity of the foam can be adjusted to be in a desired range.

The shape of polypropylene used as a material is preferably pellet or powder. Pellet-shaped polypropylene has morphological properties such as spherical, hemispherical, almond-shaped, columnar, prismatic, plate-shaped, and flake-shaped. The powdered polypropylene is obtained by crushing the above pelletized polypropylene into a powder. The powdered polypropylene preferably has a particle size of 2 mm or less.

The shape of the foam of the present embodiment is preferably a shape in which a plurality of granular foam particles are connected in a string shape or a strand shape. The granular foam particles constituting the beaded foam are preferably spherical. However, the granular foam particles do not have to be true spheres, and may be elliptical spheres or have irregularities on the surface. The foam of the present embodiment can be used by cutting and processing into various sizes. For example, in the case of a beaded foam, it may be divided into individual granular foam particles for use. Further, in the case of a strand-shaped foam, it may be cut and used as granular granular foam particles, or a plurality of strand-shaped foams may be fused and integrated in a bundled state. You may let me use it.

The foam of the present embodiment may be composed of a composition of two components of cellulose fiber and polypropylene, or may be composed of a composition containing other components other than cellulose fiber and polypropylene. Examples of other components include flame retardants, fiber-based reinforcing materials, foaming aids, and the like. Hereinafter, the composition of the foam of the present embodiment will be described.

[First Embodiment]
The foam of the first embodiment comprises the above-mentioned cellulose fiber and the above-mentioned polypropylene. That is, the foam of the first embodiment has a cellulose fiber content in the range of 10% by mass or more and 65% by mass or less, and the balance is polypropylene. The content of the cellulose fiber is preferably in the range of 15% by mass or more and 60% by mass or less.

The foam of the first embodiment is a heat insulating material by forming a foam having a density of 70 kg / m ³ or less composed of 10% by mass or more and 65% by mass or less of cellulose fibers and 35% by mass or more and 90% by mass or less of polypropylene. It was completed based on the finding that sufficient heat insulating properties can be obtained when used as.

The foam of the first embodiment has a density of 70 kg / m ³ or less, and preferably 66 kg / m ³ or less. If the density of the foam exceeds 70 kg / m ³ , sufficient heat insulating properties may not be obtained when used as a heat insulating material. On the other hand, if the density of the foam is too low, the strength of the foam may be insufficient and the application may be limited. Therefore, the density of the foam is preferably 10 kg / m ³ or more, and more preferably 15 kg / m ³ or more.

Next, the method for producing the foam of the first embodiment will be described.
The method for producing a foam of the first embodiment is a step of kneading cellulose fibers and polypropylene to produce a first kneaded product containing cellulose fibers in a range of 10% by mass or more and 65% by mass or less (first). (Kneaded product forming step), a step of kneading the first kneaded product and water to produce a second kneaded product (second kneaded product forming step), and evaporating the water content of the second kneaded product to form a foam. Includes a step of producing (foam generation step).

As a kneading device for kneading cellulose fibers and polypropylene in the first kneaded product producing step, a continuous kneader or a batch kneader can be used. Examples of the continuous kneader include a single-screw kneader and a twin-screw kneader. Examples of batch kneaders include a Banbury mixer and a pressurized kneader.

Since the densities of the cellulose fibers and polypropylene to be kneaded in the first kneading product forming step are significantly different, it is preferable to mix the cellulose fibers and polypropylene in advance to obtain a mixture before putting them into the kneading apparatus. By putting it into a kneading apparatus as a mixture of cellulose fibers and polypropylene, a first kneaded product having a uniform composition can be obtained in a short time.

In the second kneaded product forming step, it is preferable to use a continuous kneader as a kneading device for kneading the first kneaded product and water. Examples of the continuous kneader include a single-screw kneader and a twin-screw kneader. The continuous kneader preferably has a water introduction means for introducing water in the middle of the cylinder portion.

The kneading conditions such as the temperature of the cylinder part and the temperature of the die part of the continuous kneader, the screw rotation speed, and the water supply speed to the continuous kneader are the contents, materials and shapes of cellulose fibers and polypropylene, and the purpose. It can be appropriately determined according to the density range of the foam and the like.

The first kneaded product forming step and the second kneaded product forming step may be continuously performed. For example, a continuous kneader is used as a kneading device, polypropylene and cellulose fibers are put into the continuous kneader to generate a first kneaded product, and then water is supplied to the continuous kneader to perform the first kneading. A second kneaded product may be produced by kneading the product and water. By continuously performing the first kneaded product forming step and the second kneaded product forming step in this way, a second kneaded product having a uniform composition can be obtained in a relatively short time.

In the foam formation step, the moisture of the second kneaded product extruded from the die portion of the continuous kneader is evaporated to generate foam. The water content of the second kneaded product can be evaporated in the atmosphere. Normally, the foam is extruded from the die portion of the continuous kneader and the water content of the second kneaded product evaporates to produce the foam of the first embodiment. The produced foam may be cut to a length suitable for the intended use, if necessary.

The foam of the first embodiment described above is a foam having a density of 70 kg / m ³ or less, which is composed of 10% by mass or more and 65% by mass or less of cellulose fibers and 35% by mass or more of polypropylene. Therefore, the thermal conductivity is low, and sufficient heat insulating properties can be obtained when used as a heat insulating material.
Further, according to the method for producing a foam of the present embodiment, a second kneaded product obtained by kneading water with a first kneaded product containing cellulose fibers in a range of 10% by mass or more and 65% by mass or less. Since the water is evaporated to produce a foam, a foam having a large amount of foam can be obtained.

[Second Embodiment]
The foam of the second embodiment contains the cellulose fiber, the polypropylene, and the resin additive.

The foam of the second embodiment has a low density by forming a foam containing cellulose fibers, polypropylene, and a specific resin additive in a specific content, and has sufficient heat insulating properties when used as a heat insulating material. It was completed based on the knowledge that

Resin additives include vinyl resin, polystyrene resin, polyester resin, polyamide resin, acrylic resin, polyether resin, polyimide resin, elastomer resin, sulfur-containing resin, phenol resin and epoxy resin. At least one species selected from the group consisting of.

Vinyl-based resins used as resin additives include polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA), ethylene / vinyl acetate copolymer (EVA), and ethylene trifluoride (PCTFE). ), Ethylene tetrafluoride (PTFE), ethylene tetrafluoride / propylene hexafluoride copolymer (FEP), ethylene tetrafluoride / perfluoroalkoxyethylene copolymer (PFA), ethylene tetrafluoride / ethylene copolymer weight Examples thereof include coalescence (ETFE), vinylidene fluoride (PVDF), polyethylene (PE) and the like.
The vinyl-based resin is a resin having a polymerization unit represented by the formula (1), and preferably has a weight average molecular weight of 10,000 to 200,000,000. The arrangement order of [CR ₁ (R ₂ ) -CR ₃ (R ₄ )] and [CR ₅ (R ₆ ) -CR ₇ (R ₈ )], which are the repeating units in the formula (1), is particularly limited. There is no. Therefore, the formula (1) may include any of a random copolymer, a block copolymer, and an alternating copolymer.

In formula (1), R ₁ , R ₂ , R ₃ , R _4, R ₅ , R ₆ , R ₇ , and R ₈ are independently hydrogen atom, halogen atom, hydroxyl group (-OH), and acetyloxy. It is any one group selected from a group (-OCOCH ₃ ), a trifluoromethyl group (-CF ₃ ), a trifluoromethoxy group (-OCF ₃ ), and a linear or cyclic alkyl group having 1 to 10 carbon atoms. .. _{R 1, R 2, R 3} , R 4, R 5, R 6, R 7, and _{R 8} may be all different groups, some or all may be the same group. l is 40 to 100 mol%. m is 0 to 60 mol%.

Examples of the polystyrene-based resin include polystyrene (PS), styrene-acrylonitrile copolymer (AS), and styrene-butadiene-acrylonitrile copolymer (ABS).
The polystyrene-based resin is a resin having a polymerization unit represented by the formula (2), and preferably has a weight average molecular weight of 2,000 to 4,000,000. The order of arrangement of the repeating units in the equation (2) is not particularly limited. Therefore, the formula (2) may include any of a random copolymer, a block copolymer, and an alternating copolymer.

In formula (2), Ph represents a phenyl group. x is 0 to 95 mol%. y is 0 to 95 mol%. z is 5 to 100 mol%.

Examples of the polyester-based resin include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).
The polyester-based resin is preferably a resin represented by the formula (3), and preferably has a weight average molecular weight of 1,000 to 1,000,000.

In formula (3), p is 1 or 2. r is 2 to 10,000.

Examples of the polyamide resin include nylon 6, nylon 6, 6, nylon 12, and the like.
The polyamide-based resin is preferably a resin represented by the formula (4) or the formula (5), and preferably has a weight average molecular weight of 500 to 5,000,000.

In formula (4), q is 4 to 10. s is 2 to 30,000.

In formula (5), g is 2-5. h is 2 to 10. t is 2 to 30,000.

Examples of the acrylic resin include polymethylmethacrylate (PMMA), methyl methacrylate / styrene copolymer (MS) and the like.
The acrylic resin is a resin having a polymerization unit represented by the formula (6), and preferably has a weight average molecular weight of 1,000 to 3,000,000. The order of arrangement of the repeating units in the equation (6) is not particularly limited. Therefore, the formula (6) may include any of a random copolymer, a block copolymer, and an alternating copolymer.

In formula (6), R ₉ is any one group selected from a hydrogen atom and an alkyl group having 1 to 5 carbon atoms. Ph represents a phenyl group. i is 5 to 100 mol%. u is 0 to 95 mol%.

Examples of the polyether resin include polyacetal (POM), polyphenylene ether (PPE), polyetherketone (PEK), polyetheretherketone (PEEK), polyethersulfone (PES), and the like.
The polyether resin is preferably a resin having a polymerization unit represented by the formula (7), and preferably has a weight average molecular weight of 500 to 2,000,000.
In the polymerization unit represented by the formula (7), examples of the substituent include a carbonylphenyl group, a phenyl group, a sulfonylphenyl group and the like.

Wherein (7), A is, -CH ₂ -, or one or more substituents which may phenylene group having a _(-C 6 _{H 4} -) is.

The polyimide-based resin is preferably a resin represented by the formula (8), and preferably has a weight average molecular weight of 1,000 to 9,000,000.

In the formula (8), Ar is a group represented by the following formula (9) or the following formula (10). R ₁₀ is any group represented by the following formulas (11) to (15). w is 1 to 30,000.

Examples of the elastomer resin include polycarbonate (PC) and the like.
Examples of the sulfur-containing resin include polysulfone (PSF) and polyphenylene sulfide (PPS).
Examples of the phenolic resin include novolak resin and resole resin.
Examples of the epoxy resin include a copolymer of bisphenol A and epichlorohydrin.

The resin additive contained in the foam of the present embodiment may be a polymer alloy or a polymer blend in which a plurality of the above resins are mixed.
Among the above, the resin additives include polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA), ethylene / vinyl acetate copolymer (EVA), polyethylene (PE), and polystyrene (PS). , At least one selected from styrene / acrylonitrile copolymer (AS), styrene / butadiene / acrylonitrile copolymer (ABS), polyvinylidene methacrylate (PMMA), and methyl methacrylate / styrene copolymer (MS). Is preferable.

In particular, it is preferable to use at least one selected from polystyrene (PS), styrene-acrylonitrile copolymer (AS), and styrene-butadiene-acrylonitrile copolymer (ABS) as the resin additive. By using these resins as the resin additive, a foam having a lower density can be obtained.

The foam of the second embodiment may be formed only of cellulose fibers, polypropylene, and a resin additive, or may contain other components, if necessary.
Examples of other components include flame retardants, fiber-based reinforcing materials, foaming aids, and the like.
The content of the other components can be, for example, in the range of 0.1% by mass or more and 30% by mass or less as the content with respect to the total amount of the foam.

The foam of the second embodiment has a cellulose fiber content of 10% by mass or more and 65% by mass or less, a resin additive content of 0.1% by mass or more and 30% by mass or less, and a polypropylene content. Is 5% by mass or more.

The content of the cellulose fiber is preferably 10% by mass or more and 65% by mass or less, and preferably 30% by mass or more and 60% by mass or less. When the content of the cellulose fibers is 10% by mass or more, a foam having a low density can be obtained. Further, when the content of the cellulose fiber is 65% by mass or less, the content of the resin additive and polypropylene can be sufficiently secured, and the strength of the foam is not insufficient.

The content of the resin additive is 0.1% by mass or more and 30% by mass or less, and preferably 1% by mass or more and 4% by mass or less. When the content of the resin additive is 0.1% by mass or more, the effect of improving the foaming ratio by containing the resin additive can be sufficiently obtained. Further, when the content of the resin additive is 30% by mass or less, the content of the cellulose fiber and polypropylene can be sufficiently secured, and the adverse effect due to the excessive content of the resin additive does not occur.

The content of polypropylene is 5% by mass or more, preferably 20% by mass or more. When the polypropylene content is 5% by mass or more, a foam having sufficient strength can be obtained.
The content of cellulose fiber, resin additive and polypropylene in the foam can be regarded as the same as the ratio of the content of cellulose fiber, resin additive and polypropylene used as the material of the foam.

The foam of the second embodiment preferably has a density of 70 kg / m ³ or less, and more preferably 66 kg / m ³ or less. When the density of the foam is 70 kg / m ³ or less, it is suitable as a heat insulating material. On the other hand, if the density of the foam is too low, the strength of the foam may be insufficient and the application may be limited. Therefore, the density of the foam is preferably 10 kg / m ³ or more, and more preferably 15 kg / m ³ or more.

<Manufacturing method of foam>
Next, the method for producing the foam of the present embodiment will be described.
In the method for producing a foam of the present embodiment, cellulose fibers, a resin additive and polypropylene are kneaded, and the cellulose fibers are 10% by mass or more and 65% by mass or less, and the resin additive is 0.1% by mass or more and 30% by mass or more. Hereinafter, a step of producing a first kneaded product containing 5% by mass or more of polypropylene (first kneaded product producing step) and a step of kneading the first kneaded product and water to produce a second kneaded product (second). It includes a step of producing a kneaded product) and a step of evaporating the water content of the second kneaded product to produce a foam (foam product producing step).

(1st kneaded product forming step)
As a kneading device for kneading cellulose fibers, polypropylene, and a resin additive in the first kneaded product forming step, a continuous kneader or a batch kneader can be used. Examples of the continuous kneader include a single-screw kneader and a twin-screw kneader. Examples of batch kneaders include a Banbury mixer and a pressurized kneader.

Since the densities of the cellulose fibers, polypropylene, and the resin additive to be kneaded in the first kneaded product forming step are significantly different, the cellulose fibers, polypropylene, and the resin additive are mixed in advance to prepare a mixture before being put into the kneading apparatus. Is preferable. By putting it into a kneading apparatus as a mixture of cellulose fibers, polypropylene and a resin additive, a first kneaded product having a uniform composition can be obtained in a short time.
In the case of producing a foam containing other components as the foam of the present embodiment, in the first kneading product forming step, the other components are put into the kneading apparatus together with the cellulose fibers, polypropylene and the resin additive, and other components are added. The first kneaded product containing the ingredients is produced.

(Second kneaded product production step)
In the second kneaded product forming step, it is preferable to use a continuous kneader as a kneading device for kneading the first kneaded product and water. The kneading conditions such as the example of the continuous kneader, the temperature of the cylinder portion and the temperature of the die portion, the screw rotation speed, and the water supply speed to the continuous kneader are the same as those of the foam manufacturing method of the first embodiment described above. Same as the case. Further, as in the case of the foam manufacturing method of the first embodiment described above, the first kneaded product producing step and the second kneaded product producing step may be continuously performed. For example, a continuous kneader is used as a kneading device, and polypropylene, cellulose fibers, a resin additive, and other components contained as necessary are added to the continuous kneader to generate a first kneaded product. Next, water may be supplied to the continuous kneader to knead the first kneaded product and water to produce a second kneaded product.

(Foam formation process)
In the foam formation step, the moisture of the second kneaded product extruded from the die portion of the continuous kneader is evaporated to generate foam. The water content of the second kneaded product can be evaporated in the atmosphere. Normally, the foam is extruded from the die portion of the continuous kneader and the water content of the second kneaded product evaporates to produce the foam of the second embodiment. The produced foam may be cut to a length suitable for the intended use, if necessary.

The foam of the second embodiment described above contains 10% by mass or more and 65% by mass or less of cellulose fibers, 0.1% by mass or more and 30% by mass or less of a resin additive, and 5% by mass or more of polypropylene. , Resin additives are vinyl resin, polystyrene resin, polyester resin, polyamide resin, acrylic resin, polyether resin, polyimide resin, elastomer resin, sulfur-containing resin, phenol resin, epoxy resin. At least one selected from resins. Therefore, the thermal conductivity is low, and sufficient heat insulating properties can be obtained when used as a heat insulating material.
Further, according to the method for producing a foam of the present embodiment, a second kneaded product obtained by kneading a first kneaded product containing cellulose fibers, polypropylene and a specific resin additive in a specific content and water. Since the water content of the above is evaporated to generate a foam, a foam having a large amount of foam can be obtained.

[Third Embodiment]
The foam of the third embodiment contains the cellulose fiber and the polypropylene and polyurethane. The content of cellulose fibers is in the range of 10% by mass or more and 65% by mass or less, the content of polyurethane is in the range of 1% by mass or more and less than 20% by mass, and the content of polypropylene is in the range of 15% by mass or more and 89% by mass or less. It is said to be inside. Further, the shape of the foam of the present embodiment is a shape in which a plurality of granular foam particles are connected in a string shape or a strand shape.

The foam of the third embodiment is obtained by adding water to a kneaded product containing cellulose fibers, polyurethane and polypropylene in a predetermined amount and foaming the foam to obtain a foam having high strength while having a low density. It was completed based on the knowledge that it will be possible.

Polyurethane has a function of improving the strength of the foam and the amount of foam of the foam. As the polyurethane, urethane resins such as polyester urethane, polyether urethane, and polycarbonate urethane can be used.

The polyurethane is preferably water-soluble or has a high affinity for water. Polyurethane, which has a high affinity for water, is dispersed in the entire material of the foam together with water as a foaming agent during the production of the foam, so that the strength of the foam tends to be uniform. The polyurethane used in the production of the foam is preferably a polyurethane solution or an aqueous dispersion of polyurethane (aqueous polyurethane dispersion). Further, polyurethane preferably has a decomposition temperature of 190 ° C. or higher. When the decomposition temperature is 190 ° C. or higher, the polyurethane is less likely to be decomposed and volatilized during the production of the foam.

If the content of polyurethane is too low, it may be difficult to obtain the above effects of polyurethane. On the other hand, if the content of polyurethane is too high, the content of cellulose fibers and polypropylene may be relatively low, the amount of foaming may be lowered, and the cushioning property against physical impact and the heat insulating property may be lowered.
For the above reasons, the foam of the third embodiment has a polyurethane content of 1% by mass or more and less than 20% by mass. The content of polyurethane is preferably in the range of 3% by mass or more and 15% by mass or less.

Further, if the density of the foam is too high, the amount of pores in the foam becomes relatively small, and there is a possibility that the cushioning property and the heat insulating property against physical impact are lowered. Therefore, the density of the foam of the third embodiment is 80 kg / m ³ or less, and more preferably 70 kg / m ³ or less. On the other hand, if the density of the foam is too low, the strength of the foam may decrease. Therefore, the density of the foam is preferably 10 kg / m ³ or more, and more preferably 15 kg / m ³ or more.

The foam of the third embodiment may be formed only of cellulose fibers, polypropylene and polyurethane, or may contain other components if necessary.
Examples of other components include organic flame retardants, inorganic flame retardants, antioxidants, foaming aids and the like. The content of the other components can be, for example, in the range of 0.1% by mass or more and 30% by mass or less as the content with respect to the total amount of the foam. When other components are contained, the total content of polyurethane and polypolopylene with respect to the total amount of the foam is preferably 35% by mass or more, and more preferably 40% by mass or more.

Next, the method for producing the foam of the third embodiment will be described.
The method for producing the foam of the present embodiment includes cellulose fibers (for example, used paper cellulose fibers), polypropylene (for example, pellet-shaped or powdered polypropylene), and polyurethane (for example, a polyurethane solution or an aqueous dispersion of polyurethane). A step of kneading the first kneaded product to produce a first kneaded product (first kneaded product producing step) and a step of kneading the first kneaded product and water to produce a second kneaded product (second kneaded product producing step). And a step of evaporating the water content of the second kneaded product to produce a foam (foam generation step). The first kneaded product has a cellulose fiber content of 10% by mass or more and 65% by mass or less, a polyurethane content of 1% by mass or more and less than 20% by mass, and a polypropylene content of 15% by mass or more. It is preferably in the range of 89% by mass or less. When the polyurethane content of the first kneaded product is in the range of 1% by mass or more and 10% by mass or less, beads-shaped foams are likely to be produced in the foam generation step.

(1st kneaded product forming step)
As a kneading device for kneading cellulose fibers, polyurethane, and polypropylene in the first kneaded product forming step, a continuous kneader or a batch kneader can be used. Examples of the continuous kneader include a single-screw kneader and a twin-screw kneader. Examples of batch kneaders include a Banbury mixer and a pressurized kneader.

Since the densities of the cellulose fibers, polypropylene and polypropylene to be kneaded in the first kneaded product forming step are significantly different, it is preferable to mix the cellulose fibers, polyurethane and polypropylene in advance to prepare a mixture before putting them into the kneading apparatus. By putting it into a kneading apparatus as a mixture of cellulose fibers, polyurethane and polypropylene, a first kneaded product having a uniform composition can be obtained in a short time.
In the case of producing a foam containing other components as the foam of the present embodiment, in the first kneading product forming step, the other components are put into the kneading device together with the cellulose fibers, polyurethane and polypropylene, and the other components are added. The first kneaded product containing the mixture is produced.

(Second kneaded product production step)
In the second kneaded product forming step, it is preferable to use a continuous kneader as a kneading device for kneading the first kneaded product and water. The kneading conditions such as the example of the continuous kneader, the temperature of the cylinder portion and the temperature of the die portion, the screw rotation speed, and the water supply speed to the continuous kneader are the same as those of the foam manufacturing method of the first embodiment described above. Same as the case. Further, as in the case of the foam manufacturing method of the first embodiment described above, the first kneaded product producing step and the second kneaded product producing step may be continuously performed. For example, a continuous kneader is used as a kneading device, and polypropylene, cellulose fibers, polyurethane, and other components contained as necessary are added to the continuous kneader to generate a first kneaded product, and then a first kneaded product is produced. Water may be supplied to the continuous kneader to knead the first kneaded product and water to produce a second kneaded product.

(Foam formation process)
In the foam formation step, the moisture of the second kneaded product extruded from the die portion of the continuous kneader is evaporated to generate foam. The water content of the second kneaded product can be evaporated in the atmosphere. Normally, the foam is extruded from the die portion of the continuous kneader and the water content of the second kneaded product evaporates to produce the foam of the third embodiment. The generated foam is cured by cooling such as natural cooling, then cut to a length suitable for the intended use, and used as a heat insulating material, a cushioning material, a packaging material, and the like.

The foam of the third embodiment having the above configuration has a cellulose fiber content of 10% by mass or more and 65% by mass or less, and a polyurethane content of 1% by mass or more and less than 20% by mass. Among them, since the content of polypropylene is in the range of 15% by mass or more and 89% by mass or less, it has high strength while having a low density. Further, since the foam of the third embodiment has a low density of 80 kg / m ³ or less, the cushioning property and the heat insulating property against physical impact are improved.

The foam of the present embodiment described above contains cellulose fibers and polypropylene, the content of the cellulose fibers is in the range of 10% by mass or more and 65% by mass or less, and the density is as low as 80 kg / m ³ or less. Since it is a density, it has a large amount of pores. Therefore, sufficient heat insulating properties can be obtained, and it can be advantageously used as a heat insulating material, a cushioning material, and a packaging material.
Further, the shape of the foam of the present embodiment is to be cut and processed into various shapes by forming a shape in which a plurality of granular foam particles are connected in a string shape (bead shape) or a strand shape. Can be done.

(polypropylene)
A1 (pellet polypropylene): manufactured by Japan Polypropylene Corporation, Waymax (registered trademark) MFX6, MFR (temperature: 230 ° C, load: 2.16 kg): 2.5 g / 10 minutes A2 (pellet polypropylene): Japan Polypropylene Made by Novatec Co., Ltd., MG03BD, MFR (Temperature: 230 ° C., Load: 2.16 kg): 30 g / 10 minutes A3 (Pellet polypropylene): Made by Prime Polymer Co., Ltd., Prime Polypropylene (registered trademark) , J106G, MFR (melt flow rate, temperature: 230 ° C, load: 2.16 kg) 15 g / 10 minutes A4 (pellet polypropylene): Made by Japan Polypropylene Corporation, Waymax (registered trademark) MFX8, MFR (melt flow rate, Temperature: 230 ° C, load: 2.16 kg) 1.1 g / 10 minutes

B1a (powdered polypropylene): A1 (pellet polypropylene) is pulverized using a blender (Warling, Extreme Mill MX-1200XTS), and a sieve (opening 2.0 mm, wire diameter 0.9 mm) is used. Obtained by classifying and collecting the particles under the sieve.
B1b (powdered polypropylene): A1 (pelletized polypropylene) obtained by crushing it with a medium-sized cutter mill type crusher.
B2 (powdered polypropylene): A2 (pelletized polypropylene) is pulverized using a blender (Warling, Extreme Mill MX-1200XTS), and a sieve (opening 2.0 mm, wire diameter 0.9 mm) is used. Obtained by classifying and collecting the particles under the sieve.
B3 (powdered polypropylene): A3 (pellet polypropylene) is pulverized using a blender (Warling, Extreme Mill MX-1200XTS), and a sieve (opening 2.0 mm, wire diameter 0.9 mm) is used. Obtained by classifying and collecting the particles under the sieve.
B4a (powdered polypropylene): A4 (pellet polypropylene) is pulverized using a blender (Warling, Extreme Mill MX-1200XTS), and a sieve (opening 2.0 mm, wire diameter 0.9 mm) is used. Obtained by classifying and collecting the particles under the sieve.
B4b (powdered polypropylene): A4 (pellet-like polypropylene) obtained by crushing it with a medium-sized cutter mill type crusher.

(Cellulose fiber)
C1 (waste paper cellulose fiber particles): Used paper is defibrated using a crusher (Masukoroider (stone mill type grinder) manufactured by Masuyuki Sangyo Co., Ltd.). Average particle size: 160 μm (average value of the results of measuring the dispersion liquid twice using the above method 1)
C2 (coarse crushed waste paper cellulose fiber particles): Cellulose fiber (manufactured by Kanehisa Co., Ltd., trade name: comfibe (without additives)) Average particle size: 6.3 mm (measured by the above method 2)

C3 (crushed waste paper): Obtained by cutting waste paper by the following method 3. Average particle size: 3mm-5mm
(Method 3)
Using a shredder (manufactured by Sanwa Supply Co., Ltd. (trade name: PSD-12)), used paper was cut into long paper pieces with a width of 4 mm, and the obtained long paper pieces were cut in a direction substantially orthogonal to the length direction to form a substantially square shape. .. The average particle size range was ± 1 mm of the target square (length 4 mm, width 4 mm).

C4 (waste paper cellulose fiber particles): Used paper is defibrated using a crusher (Masukoroider (stone mill type grinder) manufactured by Masuyuki Sangyo Co., Ltd.). Average particle size: 81 μm (average value of the results of measuring the dispersion liquid twice using the above method 1)
C5 (Crystallinity Cellulose Particles): Avicel PH101 Cat NO. 14204
C6 (Oil palm empty fruit bunch (EFB) cellulose fiber particles): Kraft pulped oil palm empty fruit bunch cellulose (EFB) is crushed using a crusher (Masuko Sangyo Co., Ltd., Mascoroider (stone mill type grinder)). What I got. Average particle size: 123 μm (average value of the results of measuring the dispersion liquid twice using the above method 1)
C7 (waste paper cellulose fiber particles): obtained by defibrating used paper using a crusher (cutting type small crusher). Average particle size: 79 μm (average value of the results of measuring the dispersion liquid twice using the above method 1)
C8 (waste paper cellulose fiber particles): C7 (waste paper cellulose fiber particles) that have passed through a sieve having an opening of 40 μm. Average particle size: 39 μm (average value of the results of measuring the dispersion liquid twice using the above method 1)

C9 (waste paper cellulose fiber particles): C7 (waste paper cellulose fiber particles) that have passed through a sieve with a mesh size of 100 μm and remain on a sieve with a mesh size of 40 μm. Average particle size: 77 μm (average value of the results of measuring the dispersion liquid twice using the above method 1)
C10 (waste paper cellulose fiber particles): C7 (waste paper cellulose fiber particles) that have passed through a sieve with an opening of 150 μm and remain on a sieve with an opening of 100 μm. Average particle size: 108 μm (average value of the results of measuring the dispersion liquid twice using the above method 1)
C11 (waste paper cellulose fiber particles): A product obtained by defibrating unprinted waste paper using a crusher (cutting type small crusher). Average particle size: 84 μm (average value of the results of measuring the dispersion liquid twice using the above method 1)

(Resin additive)
D1 (ABS resin): Acrylonitrile, butadiene, styrene co-weighted resin (manufactured by Denki Kagaku Kogyo Co., Ltd., DENKA (registered trademark), GR-2000) is pulverized using a blender (manufactured by Waring Co., Ltd., Extreme Mill MX-1200XTS). A product obtained by classifying using a sieve (opening 2.0 mm, wire diameter 0.9 mm) and collecting the particles under the sieve.
D2 (PE): Polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd., product name: UM8510)

D3 (PC resin): Pellet-shaped polycarbonate resin (manufactured by Taipei Idemitsu Co., Ltd., trade name: Tafflon IR2200) is crushed using a blender (manufactured by Waring, Extreme Mill MX-1200XTS), and sieved (opening 710 μm, wire diameter). The particles were classified using 0.35 mm) and the particles under the sieve were collected.
D4 (PMMA resin): Pellet-shaped polymethylmethacrylate resin (manufactured by Asahi Kasei Corporation, trade name: Delpet 60N99140) is pulverized using a blender (manufactured by Waring, Extreme Mill MX-1200XTS), and sieved (opening 850 μm,). Classified using a wire diameter of 0.50 mm), and the particles under the sieve were collected.

D5 (PS resin): Polystyrene resin (SGP10 manufactured by PS Japan Corporation) is pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.), and a sieve (opening 2.0 mm, wire diameter 0.9 mm) is formed. Obtained by classifying using and collecting the particles under the sieve.
D6 (Ethylene-α-olefin copolymer resin): Ethylene-α-olefin copolymer resin (Evolu (registered trademark) SP1022 manufactured by Prime Polymer Co., Ltd.) was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). A product obtained by classifying using a sieve (opening 1.4 mm, wire diameter 0.7 mm) and collecting the particles under the sieve.

(Polyurethane)
E1 (Aqueous Polyurethane Dispersion): ETERNAL COLL (registered trademark) UW-1005E, manufactured by Ube Industries, Ltd., an aqueous dispersion having a polyurethane concentration of 30% by mass.

(Other)
F1: Phosphate ester flame retardant (manufactured by Daihachi Chemical Industry Co., Ltd., SR2550)
F2: Boric acid (manufactured by Sigma-Aldrich, 03-2900-5-500G-J) defibrated using a crusher (Masukoroider, manufactured by Masuko Sangyo Co., Ltd.). Average particle size: 128 μm (The average particle size was measured using the following method).
F3: Obtained by defibrating sodium tetraborate (manufactured by Sigma-Aldrich, 28-2010-5-500G-J) using a crusher (manufactured by Masuyuki Sangyo Co., Ltd., mass colloider (stone mill type grinder)). thing. Average particle size: 412 μm (The average particle size was measured using the following method).

(Measuring method of average particle size of boric acid and sodium tetraborate)
Since boric acid and sodium tetraborate may dissolve in ion-exchanged water, the particle size is measured using the following measuring device under the dry measurement conditions shown below. The particle size is measured twice, an average value is calculated, and this is used as the average particle size of the sample.

Measuring device: Laser diffraction / scattering type particle size distribution measuring device (manufactured by HORIBA, Ltd., trade name: LA-950V2)
Measurement conditions; Measurement unit: Dry type
Measurement mode: One-shot mode
Compressed air: 0.3MPa
Particle size standard: Volume standard
Refractive index: 1.50-0.00i (sample refractive index)

[Example I-1]
105 g of A1 (pellet-shaped polypropylene) and 45 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed A1 and C1 were separated into 30 containers, and the separated A1 and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has an A1 content of 70% by mass and a C1 content of 30% by mass.

The above raw material mixture is put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), die part temperature Y1: 180 ° C., cylinder temperature X1 / X2 / X3 / X4: 180 ° C./180 ° C./180 ° C. / 180 ° C. (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part), after kneading under the condition of screw rotation speed of 90 rpm, extrude from the tip of the die with a diameter of 3 mm and string. A pre-kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading condition I-1. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X3 part and the X4 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X4 part of the cylinder. Two kneaded products were produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-2]
105 g of B1a (powdered polypropylene) and 45 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a and C1 were separated into 30 containers, and the separated B1a and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 70% by mass and a C1 content of 30% by mass.

The obtained raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading condition I-1. At this time, cold water (5 ° C.) is supplied from between the X3 part and the X4 part of the cylinder into the cylinder at a rate of 2 mL / min to produce the first kneaded product produced between the X1 part and the X3 part of the cylinder. , X4 part of the cylinder was kneaded with water to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-3]
101 g of B1a (powdered polypropylene), 4.5 g of B2 (powdered polypropylene), and 45 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a, B2 and C1 were separated into 30 containers, and the separated B1a, B2 and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 67% by mass, a B2 content of 3% by mass, and a C1 content of 30% by mass.

The obtained raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-2. At this time, cold water (5 ° C.) is supplied from between the X3 part and the X4 part of the cylinder into the cylinder at a rate of 2 mL / min to produce the first kneaded product produced between the X1 part and the X3 part of the cylinder. , X4 part of the cylinder was kneaded with water to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-4]
A strand-shaped foam having a circular cross section was obtained in the same manner as in Example I-3 except that C2 (coarse crushed waste paper cellulose fiber particles) was used instead of C1 (waste paper cellulose fiber particles).

[Example I-5]
67.5 g of B1a (powdered polypropylene) and 82.5 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a and C1 were separated into 30 containers, and the separated B1a and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 45% by mass and a C1 content of 55% by mass.
The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) to obtain a string-shaped precursor kneaded product (first kneaded product) in the same manner as in Example I-1.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 850 μm, wire diameter 500 μm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-3. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X3 part and the X4 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X4 part of the cylinder. Two kneaded products were produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-6]
105 g of B1a (powdered polypropylene) and 45 g of C4 (waste paper cellulose fiber particles) were weighed. The weighed B1a and C4 were separated into 30 containers, and the separated B1a and C4 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 70% by mass and a C4 content of 30% by mass.

The obtained raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading condition I-1. At this time, cold water (5 ° C.) is supplied from between the X3 part and the X4 part of the cylinder into the cylinder at a rate of 2 mL / min to produce the first kneaded product produced between the X1 part and the X3 part of the cylinder. , X4 part of the cylinder was kneaded with water to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-7]
140 g of B4a (powdered polypropylene) and 60 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B4a and C1 were separated into 30 containers, and the separated B4a and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B4a content of 70% by mass and a C1 content of 30% by mass.

The obtained raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-5. At this time, cold water (5 ° C.) is supplied from between the X3 part and the X4 part of the cylinder into the cylinder at a rate of 2 mL / min to produce the first kneaded product produced between the X1 part and the X3 part of the cylinder. , X4 part of the cylinder was kneaded with water to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-8]
140 g of B1a (powdered polypropylene) and 60 g of C5 (crystalline cellulose particles) were weighed. The weighed B1a and C5 were separated into 30 containers, and the separated B1a and C5 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 70% by mass and a C5 content of 30% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), and the die part temperature was Y1: 165 ° C., the cylinder temperature was X1 / X2 / X3 / X4: 165 ° C./165 ° C./165 ° C. After kneading under the conditions of / 165 ° C./ (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 250 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-3. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-9]
140 g of B1a (powdered polypropylene) and 60 g of C6 (waste paper cellulose fiber particles) were weighed. The weighed B1a and C6 were separated into 30 containers, and the separated B1a and C6 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 70% by mass and a C6 content of 30% by mass.
A granular first kneaded product was obtained in the same manner as in Example I-8, except that the obtained raw material mixture was used.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-5. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X3 part and the X4 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X4 part of the cylinder. Two kneaded products were produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-10]
50 g of B1a (powdered polypropylene) and 50 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a and C1 were separated into 30 containers, and the separated B1a and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 50% by mass and a C1 content of 50% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), die part temperature Y1: 168 ° C., cylinder temperature X1 / X2 / X3 / X4: 170 ° C./180 ° C./180 ° C. After kneading under the conditions of / 170 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 250 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading condition I-1. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-11]
47 g of B1a (powdered polypropylene), 3 g of B2 (powdered polypropylene), and 50 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a, B2 and C1 were separated into 30 containers, and the separated B1a, B2 and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 47% by mass, a B2 content of 3% by mass, and a C1 content of 50% by mass.
A strand-shaped foam having a circular cross section was obtained in the same manner as in Example I-10 except that the obtained raw material mixture was used.

[Example I-12]
268 g of B1a (powdered polypropylene), 12 g of B2 (powdered polypropylene), and 120 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a, B2 and C1 were separated into 30 containers, and the separated B1a, B2 and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 67% by mass, a B2 content of 3% by mass, and a C1 content of 30% by mass.
A granular first kneaded product was obtained in the same manner as in Example I-10, except that the obtained raw material mixture was used.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG, manufactured by Technobel Co., Ltd.) in which the tip die was changed from one hole with a diameter of 3 mm to a hole with a diameter of 2 mm and 10 holes, and the kneading condition I-5 was as follows. Kneaded. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 8 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 2 mm, and water was evaporated from the second kneaded product to obtain 10 strand-shaped foams having a circular cross section.

[Example I-13]
47 g of B1b (powdered polypropylene), 3 g of B2 (powdered polypropylene), and 50 g of C7 (waste paper cellulose fiber particles) were weighed. The weighed B1b, B2 and C7 were separated into 30 containers, and the separated B1b, B2 and C7 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B1b content of 47% by mass, a B2 content of 3% by mass, and a C7 content of 50% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), the die part temperature was Y1: 168 ° C, and the cylinder temperature was X1 / X2 / X3 / X4: 170 ° C / 170 ° C / 170 ° C. After kneading under the conditions of / 170 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 250 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading condition I-1. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-14]
70.5 g of B4b (powdered polypropylene), 4.5 g of B2 (powdered polypropylene), and 75 g of C7 (waste paper cellulose fiber particles) were weighed. The weighed B4b, B2 and C7 were separated into 30 containers, and the separated B4b, B2 and C7 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a B2 content of 3% by mass, and a C7 content of 50% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), die part temperature Y1: 168 ° C., cylinder temperature X1 / X2 / X3 / X4: 170 ° C./175 ° C./175 ° C. After kneading under the conditions of / 170 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 250 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-6. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-15]
70.5 g of B1b (powdered polypropylene), 4.5 g of B2 (powdered polypropylene), and 75 g of C11 (waste paper cellulose fiber particles) were weighed. The weighed B1b, B2 and C11 were separated into 30 containers, and the separated B1b, B2 and C11 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B1b content of 47% by mass, a B2 content of 3% by mass, and a C11 content of 50% by mass.
A granular first kneaded product was obtained in the same manner as in Example I-13, except that the obtained raw material mixture was used.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-7. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-16]
70.5 g of B4b (powdered polypropylene), 4.5 g of B2 (powdered polypropylene), and 75 g of C11 (waste paper cellulose fiber particles) were weighed. The weighed B4b, B2 and C11 were separated into 30 containers, and the separated B4b, B2 and C11 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a B2 content of 3% by mass, and a C11 content of 50% by mass.
A granular first kneaded product was obtained in the same manner as in Example I-14, except that the obtained raw material mixture was used.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-6. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-17]
90 g of B4b (powdered polypropylene), 45 g of C11 (waste paper cellulose fiber particles), and 15 g of F1 (phosphate ester flame retardant) were weighed. The weighed B4b, C11 and F1 were separated into 30 containers, and the separated B4b, C11 and F1 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 60% by mass, a C11 content of 30% by mass, and an F1 content of 10% by mass.

The obtained raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-8. At this time, cold water (5 ° C.) is supplied from between the X2 part and the X3 part of the cylinder into the cylinder at a rate of 2 mL / min to produce the first kneaded product produced between the X1 part and the X2 part of the cylinder. , The X3 part of the cylinder was kneaded with water to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example I-18]
50 g of B4b (powdered polypropylene) and 50 g of C7 (waste paper cellulose fiber particles) were weighed. The weighed B4b and C7 were separated into 30 containers, and the separated B4b and C7 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 50% by mass and a C7 content of 50% by mass.
A strand-shaped foam having a circular cross section was obtained in the same manner as in Example I-10 except that the obtained raw material mixture was used.

[Comparative Example I-1]
Example I-2 except that C2 (coarse crushed waste paper cellulose fiber particles) was used instead of C1 (waste paper cellulose fiber particles) and kneaded under the following kneading condition I-5 instead of kneading condition I-1. A foam was obtained in the same manner as above.

[Comparative Example I-2]
67.5 g of B1a (powdered polypropylene) and 82.5 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a and C1 were separated into 30 containers, and the separated B1a and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 45% by mass and a C1 content of 55% by mass.

The obtained raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions I-3. At this time, cold water (5 ° C.) is supplied from between the X3 part and the X4 part of the cylinder into the cylinder at a rate of 2 mL / min to produce the first kneaded product produced between the X1 part and the X3 part of the cylinder. , X4 part of the cylinder was kneaded with water to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a foam.

[Comparative Example I-3]
The foam was kneaded under the following kneading condition I-4 instead of the kneading condition I-3, and the foam was prepared in the same manner as in Comparative Example I-2, except that cold water (5 ° C.) was supplied at a rate of 1 mL / min. I tried to manufacture it, but the screw stopped during kneading and no foam was obtained.

[Comparative Example I-4]
A foam was obtained in the same manner as in Comparative Example I-2 except that C2 (coarse crushed waste paper cellulose fiber particles) was used instead of C1 (waste paper cellulose fiber particles).

[Comparative Example I-5]
A foam was obtained in the same manner as in Comparative Example I-3 except that C2 (coarse crushed waste paper cellulose fiber particles) was used instead of C1 (waste paper cellulose fiber particles).

[Comparative Example I-6]
Example I-2, except that C3 (crushed waste paper) was used instead of C2 (crusose fiber particles of coarsely crushed waste paper) and kneaded under the following kneading condition I-5 instead of kneading condition I-1. In the same manner, a foam was obtained.

[Comparative Example I-7]
A foam was obtained in the same manner as in Example I-2 except that B3 (powdered polypropylene) was used instead of B1a (powdered polypropylene).

[Comparative Example I-8]
45 g of B1a (powdered polypropylene) and 105 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a and C1 were separated into 30 containers, and the separated B1a and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 30% by mass and a C1 content of 70% by mass.
A strand-shaped foam having a circular cross section was obtained in the same manner as in Example I-1 except that the obtained raw material mixture was used.

[Comparative Example I-9]
A raw material mixture having a B1a content of 95% by mass and a C1 content of 5% by mass was obtained using 143 g of B1a (powdered polypropylene) and 7.5 g of C1 (waste paper cellulose fiber particles). A strand-shaped foam having a circular cross section was obtained in the same manner as in Comparative Example I-8.

[Comparative Example I-10]
10 g of B1a (powdered polypropylene), 40 g of B2 (powdered polypropylene), and 50 g of C1 (waste paper cellulose fiber particles) were weighed. The weighed B1a, B2 and C1 were separated into 30 containers, and the separated B1a, B2 and C1 were mixed in each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 10% by mass, a B2 content of 40% by mass, and a C1 content of 50% by mass.
A strand-shaped foam having a circular cross section was obtained in the same manner as in Example I-10 except that the obtained raw material mixture was used.

(Kneading condition I-1)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 60 rpm
(Kneading condition I-2)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 350 rpm
(Kneading condition I-3)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 90 rpm
(Kneading condition I-4)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 160 ° C / 140 ° C, screw rotation speed 30 rpm
(Kneading condition I-5)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 250 rpm
(Kneading condition I-6)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 175 ° C / 175 ° C / 170 ° C, screw rotation speed 60 rpm
(Kneading condition I-7)
Die temperature Y1: 163 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 170 ° C / 170 ° C / 166 ° C, screw rotation speed 60 rpm
(Kneading condition I-8)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 170 ° C / 170 ° C / 170 ° C, screw rotation speed 150 rpm

[Evaluation]
The density and thermal conductivity of the obtained foam were measured by the following methods. The results are shown in Table 1 together with the composition of the raw material mixture.

(Measuring method of foam density)
A strand-shaped foam is cut perpendicular to the extrusion direction using a razor (GEM, 62-0167), and a test sample for density measurement of a substantially columnar columnar length of 7 to 8 cm is prepared for each foam. Three of each were prepared. The weight and volume of each of the three test samples were measured, and the density ρ (kg / m ³ ) of each test sample was determined by the following formula (1). The average value of the densities of the three obtained test samples was calculated and used as the density of the foam. The mass M (kg) of the test sample was measured in the atmosphere, and the volume V (m ³ ) of the test sample was measured by the underwater substitution method.
ρ = M / V ・ ・ ・ (1)
M: Mass of test sample (kg), V: Volume of test sample (m ³ )

(Measuring method of thermal conductivity of foam)
The thermal conductivity of the foam was measured using a rapid thermal conductivity meter (QTM-500, manufactured by Kyoto Electronics Industry Co., Ltd.). A needle-type probe (PD-N0, manufactured by Kyoto Electronics Industry Co., Ltd.) was used as the probe of the rapid thermal conductivity meter.
The strand-shaped foam is cut perpendicular to the extrusion direction using a razor (GEM, 62-0167), and a substantially columnar test sample having a length of 7 to 8 cm is prepared, 3 for each foam. This was prepared. The test sample was allowed to stand for 12 hours in a constant temperature and humidity environment at room temperature of 23 ° C. and relative humidity of 55%. Then, in the constant temperature and humidity environment, a needle type probe was inserted approximately 35 mm from the center of the cut surface of the test sample, and the thermal conductivity was measured. In addition, the thermal conductivity of the polystyrene reference sample was measured in the same manner as the test sample.

Then, the thermal conductivity λ (W / mK) of the foam was calculated by the following formula (2).
λ = λS− (λR1-λR0) ・ ・ ・ (2)
λS: Measured value of thermal conductivity of test sample (W / mK), λR0: Default value of thermal conductivity of reference sample (W / mK), λR1: Measured value of thermal conductivity of reference sample (W / mK)
Table 1 shows the average value of the thermal conductivity measured by preparing three test samples.

The foams of Comparative Examples I-2, I-4, and I-5 had a short length rather than a strand shape. Therefore, a measurement sample for measuring the thermal conductivity could not be collected from the foams of Comparative Examples I-2, I-4, and I-5. Further, it was not possible to directly insert the needle type probe into the foam of Comparative Examples I-2, I-4, and I-5 for a predetermined length (about 35 mm). Therefore, the thermal conductivity of the foams of Comparative Examples I-2, I-4, and I-5 could not be measured. Further, the measurement sample for measuring the density collected from the foams of Comparative Examples I-2, I-4, and I-5 had a short length and a distorted shape, but the density could be measured. It was.
Further, the foams of Comparative Examples I-7 and I-10 had a small amount of foaming and were in a thin and hard state like dry spaghetti. Therefore, the needle-type probe could not be inserted into the foams of Comparative Examples I-7 and I-10, and the thermal conductivity could not be measured.

As shown in Table 1, the foams of Examples I-1 to I-18 have a density of 80 kg / m ³ or less and a thermal conductivity of 40 × 10 ^-3 W / mK or less, which are low. It was. In particular, the foams of Examples I-1 to I-17 had a density of 70 kg / m ³ or less, which was low.
On the other hand, the foams of Comparative Examples I-1, I-2, I-4 to I-10 had a density of more than 80 kg / m ³ .
In Example I-2 in which cellulose fiber particles (C1) were used as the cellulose fibers, the content of the cellulose fibers was the same, and compared with Comparative Example I-6 in which the waste paper crushed product (C3) was used as the cellulose fibers. , The density was low.

[Example II-1]
101 g of B1a (powdered polypropylene), 45 g of C1 (waste paper cellulose fiber particles), and 4.5 g of D1 (ABS resin) were weighed. The weighed B1a, C1 and D1 were separated into 30 containers, and the separated B1a, C1 and D1 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 67% by mass, a C1 content of 30% by mass, and a D1 content of 3% by mass.

The obtained raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions II-1. At this time, cold water (5 ° C.) is supplied from between the X3 part and the X4 part of the cylinder into the cylinder at a rate of 2 mL / min to produce the first kneaded product produced between the X1 part and the X3 part of the cylinder. , X4 part of the cylinder was kneaded with water to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example II-2]
Example II-1 except that C2 (coarse crushed waste paper cellulose fiber particles) was used instead of C1 (waste paper cellulose fiber particles) and kneaded under the following kneading condition II-2 instead of kneading condition II-1. In the same manner as above, a strand-shaped foam having a circular cross section was obtained.

[Example II-3]
A strand-shaped foam having a circular cross section was obtained in the same manner as in Example II-1 except that D2 (PE) was used instead of D1 (ABS resin).

[Example II-4]
70.5 g of B4b (powdered polypropylene), 75 g of C7 (waste paper cellulose fiber particles), and 4.5 g of D3 (PC resin) were weighed. The weighed B4b, C7 and D3 were separated into 30 containers, and the separated B4b, C7 and D3 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C7 content of 50% by mass, and a D3 content of 3% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), die part temperature Y1: 168 ° C., cylinder temperature X1 / X2 / X3 / X4: 170 ° C./180 ° C./180 ° C. After kneading under the conditions of / 170 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 250 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions II-3. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example II-5]
70.5 g of B4b (powdered polypropylene), 75 g of C7 (waste paper cellulose fiber particles), and 4.5 g of D4 (PMMA resin) were weighed. The weighed B4b, C7 and D4 were separated into 30 containers, and the separated B4b, C7 and D4 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C7 content of 50% by mass, and a D4 content of 3% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), die part temperature Y1: 170 ° C., cylinder temperature X1 / X2 / X3 / X4: 170 ° C./180 ° C./180 ° C. After kneading under the conditions of / 170 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 250 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions II-3. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example II-6]
70.5 g of B4b (powdered polypropylene), 75 g of C8 (waste paper cellulose fiber particles), and 4.5 g of D3 (polycarbonate resin) were weighed. The weighed B4b, C8 and D3 were separated into 30 containers, and the separated B4b, C8 and D3 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C8 content of 50% by mass, and a D3 content of 3% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), the die part temperature was Y1: 172 ° C, and the cylinder temperature was X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C. After kneading under the conditions of / 172 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 250 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions II-4. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example II-7]
70.5 g of B4b (powdered polypropylene), 75 g of C9 (waste paper cellulose fiber particles), and 4.5 g of D3 (polycarbonate resin) were weighed. The weighed B4b, C9 and D3 were separated into 30 containers, and the separated B4b, C9 and D3 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C9 content of 50% by mass, and a D3 content of 3% by mass.
A strand-shaped foam having a circular cross section was obtained in the same manner as in Example II-6 except that the obtained raw material mixture was used.

[Example II-8]
70.5 g of B4b (powdered polypropylene), 75 g of C10 (waste paper cellulose fiber particles), and 4.5 g of D3 (polycarbonate resin) were weighed. The weighed B4b, C10 and D3 were separated into 30 containers, and the separated B4b, C10 and D3 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C10 content of 50% by mass, and a D3 content of 3% by mass.
A strand-shaped foam having a circular cross section was obtained in the same manner as in Example II-6 except that the obtained raw material mixture was used.

[Example II-9]
188 g of B4b (powdered polypropylene), 200 g of C11 (waste paper cellulose fiber particles), and 12 g of D3 (polycarbonate resin) were weighed. The weighed B4b, C11 and D3 were separated into 30 containers, and the separated B4b, C11 and D3 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C11 content of 50% by mass, and a D3 content of 3% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), the die part temperature was Y1: 172 ° C, and the cylinder temperature was X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C. / 172 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part), after kneading under the condition of screw rotation speed 250 rpm, extruded from the tip of the die with a diameter of 2 mm and 7 holes. , A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG, manufactured by Technobel Co., Ltd.) equipped with a tip die having a diameter of 2 mm and 7 holes, and kneaded under the following kneading conditions II-5. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 6 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 2 mm, and water was evaporated from the second kneaded product to obtain seven strand-shaped foams having a circular cross section.

[Example II-10]
212 g of B4b (powdered polypropylene), 225 g of C6 (waste paper cellulose fiber particles), and 13.5 g of D3 (polycarbonate resin) were weighed. The weighed B4b, C6 and D3 were separated into 30 containers, and the separated B4b, C6 and D3 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C6 content of 50% by mass, and a D3 content of 3% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), die part temperature Y1: 166 ° C, cylinder temperature X1 / X2 / X3 / X4: 175 ° C / 175 ° C / 175 ° C. / 168 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part), after kneading under the condition of screw rotation speed 250 rpm, extruded from the tip of the die with a diameter of 2 mm and 7 holes. , A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 2.0 mm, wire diameter 0.9 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG, manufactured by Technobel Co., Ltd.) equipped with a tip die having a diameter of 2 mm and 7 holes, and kneaded under the following kneading conditions II-5. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 6 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 2 mm, and water was evaporated from the second kneaded product to obtain seven strand-shaped foams having a circular cross section.

[Example II-11]
64 g of B1a (powdered polypropylene), 102 g of C1 (waste paper cellulose fiber particles), 6 g of D3 (polycarbonate resin), 14 g of F2 (boric acid), and 14 g of F3 (sodium tetraborate) were weighed. The weighed B1a, C1, D3, F2 and F3 were separated into 30 containers, and the separated B1a, C1, D3, F2 and F3 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B1a content of 32% by mass, a C1 content of 51% by mass, a D3 content of 3% by mass, an F2 content of 7% by mass, and an F3 content of 7% by mass.

A granular first kneaded product was obtained in the same manner as in Example II-6 except that the obtained raw material mixture was used.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions II-6. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X3 part and the X4 part of the cylinder at a rate of 3 mL / min, and the first kneaded product and water are kneaded in the X4 part of the cylinder. Two kneaded products were produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example II-12]
94.0 g of B4b (powdered polypropylene), 100 g of C7 (waste paper cellulose fiber particles), and 6.0 g of D5 (PS resin) were weighed. The weighed B4b, C7 and D5 were separated into 30 containers, and the separated B4b, C7 and D5 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C7 content of 50% by mass, and a D5 content of 3% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), die part temperature Y1: 168 ° C., cylinder temperature X1 / X2 / X3 / X4: 170 ° C./180 ° C./180 ° C. After kneading under the conditions of / 170 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 60 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 1.4 mm, wire diameter 0.7 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions II-3. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

[Example II-13]
94.0 g of B4b (powdered polypropylene), 100 g of C7 (waste paper cellulose fiber particles), and 6.0 g of D6 (ethylene-α-olefin copolymer resin) were weighed. The weighed B4b, C7 and D6 were separated into 30 containers, and the separated B4b, C7 and D6 were mixed for each container to obtain a raw material mixture. The obtained raw material mixture has a B4b content of 47% by mass, a C7 content of 50% by mass, and a D6 content of 3% by mass.

The above raw material mixture was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.), die part temperature Y1: 168 ° C., cylinder temperature X1 / X2 / X3 / X4: 170 ° C./180 ° C./180 ° C. After kneading under the conditions of / 170 ° C / (X1 to X4 are the temperatures of each part from the introduction part of the raw material mixture in the cylinder part to the die part) and the screw rotation speed of 60 rpm, the mixture is extruded from the tip of the die having a diameter of 3 mm. A string-shaped precursor kneaded product (first kneaded product) was obtained.

The obtained first kneaded product was cut to an appropriate length. The obtained cut piece was pulverized using a blender (Extreme Mill MX-1200XTS manufactured by Waring Co., Ltd.). The obtained pulverized product was classified using a sieve (opening 1.4 mm, wire diameter 0.7 mm), and the granular first kneaded product under the sieve was recovered.

The obtained granular first kneaded product was put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) and kneaded under the following kneading conditions II-3. At this time, cold water (5 ° C.) is supplied into the cylinder from between the X2 part and the X3 part of the cylinder at a rate of 2 mL / min, and the first kneaded product and water are kneaded in the X3 part of the cylinder. 2 A kneaded product was produced. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a strand-shaped foam having a circular cross section.

(Kneading condition II-1)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 250 rpm
(Kneading condition II-2)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 150 rpm
(Kneading condition II-3)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 60 rpm
(Kneading condition II-4)
Die temperature Y1: 172 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 172 ° C, screw rotation speed 60 rpm
(Kneading condition II-5)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 175 ° C / 175 ° C / 175 ° C / 168 ° C, screw rotation speed 150 rpm
(Kneading condition II-6)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 90 rpm

[Evaluation]
The density and thermal conductivity of the obtained foam were measured by the above method. The results are shown in Table 2 together with the composition of the raw material mixture.

As shown in Table 2, the foams of Examples II-1 to II-13 containing the resin additive have a density of 70 kg / m ³ or less and a thermal conductivity of 40 × 10 ^-3 W / mK or less. Yes, it was low.

[Example III-1]
B1a (powdered polypropylene) 103.5 g, C1 (waste paper cellulose fiber) 45 g, and E1 (aqueous polyurethane dispersion) 5.0 g (1.5 g as polyurethane) were weighed. The weighed B1a, C1 and E1 were separated into 30 containers, and the separated B1a, C1 and E1 were mixed in each container to obtain a raw material mixture. The composition of the obtained raw material mixture has a B1a content of 69% by mass, a C1 content of 30% by mass, and an E1 content of 1% by mass.

The obtained raw material mixture is put into a twin-screw kneading extruder (KZW15-30MG manufactured by Technobel Co., Ltd.) in which the part from the introduction part of the raw material mixture in the cylinder part to the die part is divided into four areas X1 to X4. , Kneaded under the following kneading conditions III-1. At this time, cold water (5 ° C.) is supplied from between X3 and X4 of the cylinder portion into the cylinder portion at a rate of 2 mL / min to generate a first kneaded product between X1 to X3 of the cylinder portion to generate the cylinder. The first kneaded product and water were kneaded in part X4 to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a foam. The obtained foam was in the shape of beads in which a plurality of granular foam particles were connected in a string shape.

[Example III-2]
As a raw material mixture, 90 g of B1a (powdered polypropylene), 45 g of C1 (waste paper cellulose fiber), and 50 g of E1 (aqueous polyurethane dispersion) (15 g as polyurethane) were weighed in the same manner as in Example III-1. The foam was produced. The obtained foam was in the shape of beads in which a plurality of granular foam particles were connected in a string shape. The composition of the raw material mixture is such that the B1a content is 60% by mass, the C1 content is 30% by mass, and the E1 content is 10% by mass.

[Example III-3]
Examples III-, except that 82.5 g of B1a (powdered polypropylene), 45 g of C1 (waste paper cellulose fiber), and 75 g of E1 (aqueous polyurethane dispersion) (22.5 g as polyurethane) were weighed as the raw material mixture. A foam was produced in the same manner as in 1. The obtained foam had a strand shape with a circular cross section. The composition of the raw material mixture is such that the B1a content is 55% by mass, the C1 content is 30% by mass, and the E1 content is 15% by mass.

[Example III-4]
Examples of B1a (powdered polypropylene) 85.5 g, B2 (powdered polypropylene) 4.5 g, C1 (waste paper cellulose fiber) 45 g, and E1 (aqueous polyurethane dispersion) 50 g (15 g as polyurethane) were weighed. The raw material mixture was obtained by mixing in the same manner as in III-1. The composition of the obtained raw material mixture is 57% by mass of B1a content, 3% by mass of B2 content, 30% by mass of C1 content, and 10% by mass of E1 content.

The obtained raw material mixture was put into a twin-screw kneading extruder (manufactured by Technobel Co., Ltd., KZW15-30MG) and kneaded under the following kneading conditions III-2. At this time, cold water (5 ° C.) is supplied from between X3 and X4 of the cylinder portion into the cylinder portion at a rate of 5 mL / min to generate a first kneaded product between X1 to X3 of the cylinder portion. The first kneaded product and water were kneaded in part X4 to produce a second kneaded product. The produced second kneaded product was extruded from the tip of a die having a diameter of 3 mm, and water was evaporated from the second kneaded product to obtain a foam. The obtained foam was in the shape of beads in which a plurality of granular foam particles were connected in a string shape.

[Comparative Example III-1]
As a raw material mixture, 75 g of B1a (powdered polypropylene), 45 g of C1 (waste paper cellulose fiber), and 100 g of E1 (aqueous polyurethane dispersion) (30 g as polyurethane) were weighed and mixed in the same manner as in Example III-1. A foam was produced in the same manner as in Example III-1 except that the obtained mixture was used. The obtained foam had an indefinite shape having a plurality of bump-shaped bulging protrusions. The composition of the raw material mixture is such that the B1a content is 50% by mass, the C1 content is 30% by mass, and the E1 content is 20% by mass.

(Kneading condition III-1)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 60 rpm
(Kneading condition III-2)
Die temperature Y1: 168 ° C, cylinder temperature X1 / X2 / X3 / X4: 170 ° C / 180 ° C / 180 ° C / 170 ° C, screw rotation speed 350 rpm

[Evaluation]
The density and tensile specific energy of the foam obtained were measured. The density of the foam was measured by the above method. The tensile breaking specific energy of the foam was measured by the following method. The results are shown in Table 3 together with the composition of the raw material mixture. In addition, the tensile breakthrough specific energy was also measured for the foam prepared in Example I-2. The results are shown in Table 3.

(Measuring method of tensile breakthrough specific energy of foam)
The tensile breaking energy of the foam was measured using a universal testing machine (manufactured by Shimadzu Corporation, EZ-LX). Three test samples were prepared by cutting the strand-shaped test sample into a columnar shape and the bead-shaped test sample by cutting the connecting portion of the granular foam particles to a length of 8 cm. The test sample was attached between the jigs of the universal testing machine (distance between jigs 5 cm) and a tensile test was performed to create a stress-strain curve. From the obtained area values under the stress-strain curve, the tensile breaking energy U (Nm) was determined using the analysis software (Trapezium X Ver 1.4.0) attached to the universal testing machine.
The tensile breaking specific energy Us (Nm / g) was calculated by the following formula (3). In addition, Table 3 shows the average value of the tensile breakthrough specific energies measured by preparing three test samples.
Us = U / Mi ... (3)
Mi: Mass of test sample attached between jigs (distance between jigs 5 cm), U: Tensile breaking energy (Nm)

It was confirmed that the foams of Examples III-1 to III-4 containing polyurethane within the scope of the present invention have a higher tensile specific energy at break than the foams of Example I-2 containing no polyurethane. It was. In addition, the foam of Comparative Example III-1 containing more polyurethane than the range of the present invention had a significantly reduced tensile breakthrough specific energy. It is considered that this is because the density of the foam becomes too high due to the large amount of polyurethane.

The foam of the present invention can be advantageously used as a heat insulating material, a cushioning material, and a packaging material.

Claims (6)

Contains cellulose fibers and polypropylene
The content of the cellulose fiber is in the range of 10% by mass or more and 65% by mass or less.
A foam having a density of 80 kg / m ³ or less. The foam according to claim 1, wherein a plurality of granular foam particles are connected in a string shape or in a strand shape. It is composed of the cellulose fiber and the polypropylene.
The foam according to claim 1, which has a density of 70 kg / m ³ or less. In addition, it contains a resin additive and
The resin additives are vinyl-based resin, polystyrene-based resin, polyester-based resin, polyamide-based resin, acrylic-based resin, polyether resin, polyimide-based resin, elastomer-based resin, sulfur-containing resin, phenol-based resin, and epoxy-based resin. At least one selected from the group consisting of resins,
The content of the resin additive is 0.1% by mass or more and 30% by mass or less.
The foam according to claim 1, wherein the polypropylene content is 5% by mass or more. The foam according to claim 4, which has a density of 70 kg / m ³ or less. In addition, it contains polyurethane
The content of the polyurethane is in the range of 1% by mass or more and less than 20% by mass.
The foam according to claim 1, wherein the polypropylene content is in the range of 15% by mass or more and 89% by mass or less.