JP2010174192A - Polyolefin resin foam-molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyolefin resin foam molded-product which is formed relatively simply and has a relatively small cell diameter. <P>SOLUTION: The polyolefin resin foam-molded product is produced by foaming and extruding a polyolefin resin composition including at least either a polyethylene resin or a polypropylene resin and at least one kind of a cell-forming agent. The polyolefin resin composition further includes an acrylic resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyolefin resin foam molded article formed of a polyolefin resin composition containing at least one of a polyethylene resin and a polypropylene resin and a cell forming agent.

  Conventionally, polyolefin resin foam moldings are not only formed using relatively inexpensive materials such as polyethylene resins and polypropylene resins, but also because these resins are excellent in moldability and workability. It is commercially available as a low cost and low cost product.

  In particular, the polyolefin resin open-cell foamed molded products, in which the bubbles are not independent but connected to each other, have the property of absorbing sound and absorbing water. It is suitably used as a gap filling material for products, an anti-condensation material for air conditioners, and a soundproofing material for wooden floors.

  In such open-cell foamed molded products and foamed molded products such as closed-cell foamed molded products, when the cell diameter is increased, the appearance is reduced, such as rough skin, and the mechanical strength is decreased. Conventionally, it is required to form finer bubbles.

  However, in a polyolefin resin foam-molded article obtained by foam-molding a polyolefin resin, it is difficult to reduce the cell diameter by a simple method, and the above-mentioned demand has not been sufficiently satisfied (Patent Document 1). ).

JP 2006-257307 A

  An object of the present invention is to provide a polyolefin resin foam molded article that can be formed relatively easily and has a relatively small cell diameter in view of the above-described problems.

  In the present invention relating to a polyolefin resin foam molded article for solving the above-mentioned problems, a polyolefin resin composition containing at least one of a polyethylene resin and a polypropylene resin and a cell forming agent is foam-extruded. The polyolefin-based resin foam molded article is characterized in that the polyolefin-based resin composition further contains an acrylic resin.

In the polyolefin resin foam molded article having such a configuration, since the compatibility of the acrylic resin with the polyethylene resin or polypropylene resin is low, the polyolefin resin foam molded article is subjected to foam extrusion with the polyolefin resin composition. In addition, the acrylic resin is relatively highly dispersed in the matrix containing the polyethylene resin or the polypropylene resin, and a so-called “sea-island structure” can be formed.
And although the mechanism of action is not completely elucidated, it is considered that the acrylic resin dispersed in the polyolefin resin composition can function as an agent for promoting the generation of relatively small bubbles. That is, during foam molding, it is considered that foaming with a relatively highly dispersed acrylic resin as a core is promoted, and as a result, fine bubbles are easily generated.

  In the polyolefin resin foam molded article of the present invention, by the relatively simple technique of containing an acrylic resin in the polyolefin resin composition to be used, fine bubbles are likely to occur during foam molding, and relatively small bubbles. There is an effect that it becomes easy to form a polyolefin-based resin foam-molded article containing the.

The figure which shows the bubble formation condition of the foam sheet of the comparative example 1 (SEM photograph). The figure which shows the bubble formation condition of the foam sheet of Example 1 (SEM photograph).

As an embodiment according to the present invention, a polyolefin resin foam molded article will be described below.
First, the polyolefin resin composition for forming the polyolefin resin foam molded article of this embodiment will be described.

  The polyolefin-based resin composition contains a polyolefin-based base resin containing at least one of a polyethylene-based resin and a polypropylene-based resin, and a cell-forming agent that forms bubbles in a molded body, and further includes an acrylic resin Contains resin.

Examples of the polyethylene (PE) resin include high density polyethylene resin, medium density polyethylene resin, linear low density polyethylene resin, and low density polyethylene resin (obtained by a high pressure method).
Examples of the polypropylene (PP) resin include a homopolypropylene resin composed only of a propylene component, and a random copolymer and a block copolymer containing an olefin component such as ethylene in addition to the propylene component.
In the case of a copolymer, it is desirable to use an olefin other than propylene containing 0.5 to 30% by weight, particularly preferably 1 to 10% by weight, in the copolymer. Examples of the olefin component in this case include ethylene or an α-olefin having 4 to 10 carbon atoms.

In particular, when a copolymer is employed as the polypropylene resin, an olefin component other than propylene is contained in the copolymer in a proportion of 0.5 to 30% by weight, particularly 1 to 10% by weight. Is preferred.
Examples of the olefin in this case include ethylene or an α-olefin having 4 to 10 carbon atoms.
In particular, a high melt tension polypropylene resin excellent in foamability is preferable, and for example, those described in Japanese Patent No. 2521388 can be suitably used.

  In addition to these, polyolefin resins such as polybutene resin and poly-4-methylpentene-1 resin are included in the polyolefin resin composition as long as the effects of the present invention are not significantly reduced. It can be contained as a part.

As the acrylic resin, a polymer obtained by using (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylamides, and (meth) acrylonitrile as main monomer components can be used.
In this specification, the term “(meth) acryl” is used to include both “methacryl” and “acryl”.

More specifically, examples of the monomer component constituting the acrylic resin include acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester.
Examples of the acrylate ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, hexyl acrylate, and n-octyl acrylate. Alkyl acrylates having 1 to 18 carbon atoms in the alkyl group, such as 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, palmityl acrylate, or cyclohexyl acrylate. In addition, methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, and methacrylate. Alkyl groups such as hexyl acrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, palmityl methacrylate and cyclohexyl methacrylate have about 1 to 18 carbon atoms. And methacrylic acid alkyl esters.

  Furthermore, as a monomer component constituting the acrylic resin, (meth) acrylic acid such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, etc. An alkyl ester having a hydroxyl group in the side chain of the (meth) acrylic acid side chain such as methoxybutyl acrylate, methoxybutyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, ethoxybutyl acrylate, ethoxybutyl methacrylate, etc. Alkyl ester having alkoxyl group; Alkenyl ester of (meth) acrylic acid such as allyl acrylate and allyl methacrylate; allyloxyethyl acrylate and allyloxyethyl methacrylate Alkenyloxyalkyl esters of (meth) acrylic acid such as glycidyl acrylate, glycidyl methacrylate, and alkyl esters having an epoxy group in the side chain of acrylic acid such as methyl glycidyl acrylate and methyl glycidyl methacrylate; acrylic Mono- or di-alkylaminoalkyl esters of (meth) acrylic acid such as diethylaminoethyl acid, diethylaminoethyl methacrylate, methylaminoethyl acrylate, methylaminoethyl methacrylate; silyl group, alkoxysilyl group or hydrolysis as side chain And silicone-modified (meth) acrylic acid ester having a functional alkoxysilyl group.

  In addition, examples of the monomer component constituting the acrylic resin include acrylamides and methacrylamides, such as acrylamide and methacrylamide. Specifically, (meth) acrylamide having a methylol group such as N-methylolacrylamide and N-methylolmethacrylamide; N-alkoxymethylolacrylamide (for example, N-isobutoxymethylolacrylamide), and N-alkoxymethylolmethacrylamide (Meth) acrylamide having an alkoxymethylol group such as (for example, N-isobutoxymethylol methacrylamide); (Meth) acrylamide having an alkoxyalkyl group such as N-butoxymethyl acrylamide or N-butoxymethyl methacrylamide be able to.

In addition, various acrylic monomers such as acrylonitrile and methacrylonitrile can be cited as monomer components constituting the acrylic resin.

These monomer components can be used alone or in combination.
That is, even if the acrylic resin used in the present invention is a homopolymer composed only of any of the various monomer components exemplified above, a copolymer formed by combining a plurality of the various monomer components exemplified above. (Copolymer) may be used.
Furthermore, in this embodiment, a copolymer containing another monomer component in addition to the monomer component can be used as the acrylic resin.

  The monomer component other than those exemplified above is not particularly limited as long as it forms a copolymer with the monomer component. For example, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl lactate, vinyl butyrate, versatic acid Examples thereof include vinyl monomers such as vinyl and vinyl benzoate, ethylene, butadiene, and styrene.

As the acrylic resin in the present embodiment, a polymethyl methacrylate (PMMA) resin is preferable among those using one or more of the above acrylic monomer components.
Further, an ethylene-acrylic acid copolymer (EAA) resin is suitable as long as it is a copolymer of a monomer component other than the acrylic monomer and the acrylic monomer component.

  The bubble-forming agent is used for forming bubbles when a polyolefin-based resin foam molded article is produced using a polyolefin-based resin composition. Examples of such bubble forming agents include bubble nucleating agents for forming bubbles, blowing agents, and compound particles that generate gas by thermal decomposition.

  The bubble nucleating agent is not particularly limited as long as it is generally used as a bubble nucleating agent. For example, talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, Examples include inorganic compounds such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, barium sulfate, and glass beads, and organic compounds such as polytetrafluoroethylene. Talc is particularly preferable. In addition, a bubble nucleating agent may be used independently or 2 or more types may be used together.

  As the foaming agent, those conventionally used for foaming extrusion can also be employed in this embodiment. For example, water, hydrocarbons, various chlorofluorocarbons, dimethyl ether, methyl chloride, ethyl chloride, nitrogen, carbon dioxide Argon, etc. can be used. These foaming agents can be used with the cell nucleating agent.

  Moreover, as the compound particles that generate gas by thermal decomposition, for example, azodicarbonamide, sodium hydrogen carbonate, a mixture of sodium hydrogen carbonate and citric acid, or the like can be used.

The amount of the acrylic resin relative to the polyolefin resin composition is usually 5 to 20% by weight, and preferably 5 to 15% by weight.
When the amount of the acrylic resin is 5% by weight or more with respect to the polyolefin resin composition, there is an advantage that fine bubbles are more easily formed. There is an advantage that the influence on the physical properties of the polyolefin-based resin foam molded article is reduced.

  Although not described in detail here, the polyolefin resin composition used for forming the polyolefin resin foam molded article of the present embodiment contains a compounding agent used for forming a general polymer foam molded article. For example, various stabilizers such as antistatic agents, weathering agents and anti-aging agents, processing aids such as lubricants, slip agents, antifogging agents, pigments, fillers and the like can be appropriately added as additives.

Examples of the antistatic agent include polyethylene oxide, polypropylene oxide, polyethylene glycol, polyester amide, polyether ester amide, and copolymers of olefin blocks and hydrophilic blocks described in JP-A No. 2001-278985. Examples thereof include molecular type antistatic agents.
Examples of the antistatic agent include alkylbenzene sulfonates, for example, anionic surfactants such as sodium dodecylbenzene sulfonate, other surfactants, and low molecular weight antistatic agents such as alkali metal salts. .

The average cell diameter in the polyolefin resin foam molded article can be appropriately adjusted by adjusting the amount of the acrylic resin or adjusting the conditions of foam extrusion described later.
The average cell diameter is preferably 0.2 mm or less in that the smoothness of the surface of the molded body and the light impermeability of the molded body can be improved.

The average cell diameter refers to that measured in accordance with the test method of ASTM D2842-69.
Specifically, the foamed molded body is first cut along the MD direction (extrusion direction) and the TD direction (direction orthogonal to the extrusion direction), and the center of each cut surface is scanned by an electron microscope (manufactured by Hitachi, Ltd.). The product name “S-3000N”) is magnified 20 times (in some cases, 100 times) and photographed.
Next, the photographed image is printed on A4 paper, and a straight line having a length of 60 mm is drawn on the image. In addition, about the cut surface cut | disconnected in MD direction, a straight line is drawn in parallel with MD direction, and about the cut surface cut | disconnected in TD direction, a straight line is drawn in parallel with TD direction.
Further, the average chord length (t) of the bubbles is calculated from the number of bubbles existing on the straight line by the following formula (1), and the average chord length is calculated as the average bubble diameter in each direction (MD direction, TD direction, VD direction). And Then, an arithmetic average value of the obtained bubble diameter in the MD direction (D _MD ) and the bubble diameter in the TD direction (D _TD ) is defined as the average cell diameter of the polyolefin resin foam molded article.
Average bubble diameter (mm) = (D _MD + D _TD ) / 2 (1)

  The density of the bubbles in the polyolefin resin foam molded article can be appropriately adjusted by adjusting the amount of the acrylic resin or adjusting the conditions of foam extrusion described later.

In addition, this bubble density (X: piece / cm < ³ >) does not foam a resin composition based on the average bubble diameter (C: mm) measured based on the test method of ASTM D2842-69, and JIS K7112-1999. Calculate the following formula (2) from the density when measured in the state (ρ: kg / m ³ ) and the apparent density (D: kg / m ³ ) of the foamed molded article measured based on JIS K7222-1999. Can be obtained.
Bubble density X = (ρ / D−1) / {(4/3) · π · (C / 10/2) ³ } (2)

In general, polyolefin resin foam moldings can be expected to improve aesthetics and mechanical strength as the bubbles are made finer. On the other hand, if the bubbles are made finer, it becomes difficult to achieve a high foaming ratio and impart light weight. May be difficult.
For this reason, the foam density of the polyolefin resin foam in this embodiment is preferably 1 × 10 ⁶ / cm ³ or more and less than 1 × 10 ¹¹ / cm ^3. It is more preferably ⁷ pieces / cm ³ or more and less than 5 × 10 ¹⁰ pieces / cm ³ , and further preferably 5 × 10 ⁷ pieces / cm ³ or more and less than 5 × 10 ⁹ pieces / cm ³ .

Next, a production method for producing a polyolefin resin foam molded article using such a polyolefin resin composition will be described by taking a case of producing a foam sheet as an example.
In the present embodiment, a method used in a general foam sheet manufacturing method can be employed. For example, a polyolefin resin composition containing the base resin, the acrylic resin, and a cell nucleating agent is used. After carrying out the resin kneading step to be produced, a method of carrying out an extrusion step of extruding and foaming the obtained polyolefin-based resin composition into a sheet can be adopted.
Below, each process is demonstrated more concretely.

(Resin kneading process)
First, base resin, acrylic resin, polymer antistatic agent, bubble nucleating agent and, if necessary, additives such as slip agent and antifogging agent are weighed and dried with a tumbler blender, Henschel mixer, etc. After blending, each compounded material is melt-kneaded so as to be in a substantially uniform mixed state using a single-screw extruder, a multi-screw extruder, a kneader, a Banbury mixer, or the like.
Thereafter, the kneaded product is extruded into a strand shape and pelletized, or hot cut and pelletized to produce a pellet made of a polyolefin resin composition.

(Extrusion process)
Examples of the method of foaming and extruding the pellets obtained in the resin kneading step to process into a foamed sheet include a method of extruding from a circular die or a T-die to form a sheet.
More specifically, in the foam sheet manufacturing method of the present embodiment, there is a method for producing a foam sheet by using a tandem type extruder that allows easy adjustment of extrusion conditions, and attaching a circular die or the like to the tandem type extruder. Can be mentioned.
By using a tandem type extruder, for example, a kneading zone is provided in the first stage extruder so that the resin pressure is set at a slightly low pressure so that a blowing agent such as carbon dioxide can be easily pressed into the kneading zone. Or by setting the temperature to a high temperature to increase the solubility of the foaming agent, the foaming agent can be sufficiently dispersed in the polyolefin resin composition, and the temperature setting of the second stage extruder is compared with the first stage. Thus, the melt viscosity of the polyolefin resin composition can be adjusted to a viscosity suitable for foaming at a low temperature.

  In addition, since the width of the obtained sheet is determined by the diameter of the cooling mandrel, the circular die does not require a mold having a width equal to or larger than the product width unlike the flat die, and compared with the flat die. It is excellent in that a foam sheet having a desired width can be easily produced.

  In the resin kneading step and the extrusion step, the acrylic resin having a high polarity is dispersed in a base resin such as a polyethylene resin or a polypropylene resin having a lower polarity than the acrylic resin. A sea-island structure in which a dispersed phase is formed by the system resin is formed in the polyolefin resin composition.

In the polyolefin resin composition, it is considered that the finely dispersed acrylic resin can function as an agent that promotes the generation of relatively fine bubbles. That is, during foam molding, it is considered that foaming with a relatively highly dispersed acrylic resin as a core is promoted, and as a result, fine bubbles are easily generated.
Thus, the polyolefin resin foam sheet which has a comparatively fine bubble can be manufactured by mix | blending acrylic resin with base resin.

In the polyolefin resin composition, when the matrix containing the polyethylene resin or polypropylene resin is foamed, the tension generated by the expansion of the bubble film accompanying the growth of the bubbles is the critical tension of the polyolefin resin composition. When it exceeds, an opening is generated in the bubble film to form an “open bubble” in which the bubbles are connected.
Therefore, when the bubble film breaks in the early stage of bubble formation, the bubble diameter is increased. On the other hand, when the bubble film breaks in the later stage of bubble formation, it becomes easy to form an open-cell foamed article having open cells.
In this embodiment, the dispersed phase of the acrylic resin, which is considered to contribute to the bubble nuclei, is involved in the formation of open cells as the starting point of the bubble film breakage in the later stage of bubble formation, It tends to promote the formation of open cells as well as the formation.

  Thus, since the polyolefin resin foam sheet can be produced by a simple method of blending the acrylic resin with the base resin, a foam sheet in which fine bubbles are easily formed can be obtained.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Formulation 1)
Made by Nippon Polyolefin Co., Ltd., low density polyethylene, trade name “Novatech LF580”, MFR = 4 g / 10 min (condition K of JIS K 7210: temperature 190 ° C., nominal load 2.16 kg), manufactured by Sanyo Chemical Industries, polymer type Antistatic agent (main component: block copolymer having a polyether block and a polyolefin block in the molecule), trade name “Pelestat 300”, MFR = 30 g / 10 min (condition K of JIS K 7210: temperature 190 ° C., nominal A weight ratio of 2.16 kg) and a weight ratio of 90: 10: 0.1 (LF580: Perestat 300: PO410K = 90: manufactured by Dainichi Seika Co., Ltd., sodium bicarbonate-citrate master batch, trade name “Finecell Master PO410K”) 10: 0.1) was prepared, and this was designated “Formulation 1”.

(Formulation 2)
Made by Nippon Polyolefin Co., Ltd., low density polyethylene, trade name “Novatech LF580”, MFR = 4 g / 10 min (condition K of JIS K 7210: temperature 190 ° C., nominal load 2.16 kg), manufactured by Sanyo Chemical Industries, polymer type Antistatic agent (main component: block copolymer having a polyether block and a polyolefin block in the molecule), trade name “Pelestat 300”, MFR = 30 g / 10 min (condition K of JIS K 7210: temperature 190 ° C., nominal Load, 2.16 kg), Sumitomo Chemical Co., Ltd., PMMA, trade name “Sumipec LG35”, MFR = 35 g / 10 min (condition of JIS K 7210: temperature 230 ° C., nominal load 3.80 kg) Made by baking soda-citric acid master batch, trade name "Finecell Master PO410K" 90 5:10: 0.1 weight ratio (LF580: Pelestat 300: LG35: PO410K = 90: 5: 10: 0.1) to prepare a formulation which was formulated in, was referred to as "Formula 2".

(Comparative Example 1)
The blend 1 was subjected to foam extrusion to produce a foam sheet of Comparative Example 1 (sheet-shaped polyolefin resin foam molded article).
FIG. 1 shows a state in which a cut surface obtained by cutting the foam sheet in the thickness direction is observed with a scanning electron microscope (SEM).

Example 1
The above blend 2 was foam-extruded under the same conditions as the foamed sheet of Comparative Example 1 to prepare a foamed sheet of Example 1 (sheet-like polyolefin resin foam molded article).
FIG. 2 shows a state where a cut surface obtained by cutting the foam sheet in the thickness direction is observed with a scanning electron microscope (SEM).
2 is taken at the same magnification as FIG.

  From these figures, it can be seen that a foamed molded article having a small cell diameter can be formed by containing acrylic resin (PMMA).

Claims (2)

A polyolefin resin foam molded article obtained by foam extrusion of a polyolefin resin composition containing at least one of a polyethylene resin and a polypropylene resin and a cell forming agent,
The polyolefin resin composition further comprises an acrylic resin in the polyolefin resin composition.   The polyolefin resin foam-molded article according to claim 1, wherein at least one of a polymethyl methacrylate resin or an ethylene-acrylic acid copolymer resin is contained in the polyolefin resin composition as the acrylic resin.