KR20020005618A - Olefin polymers and alpha-olefin/vinyl or alpha-olefin/vinylidene interpolymer blend foams - Google Patents

Abstract

The present invention provides a polymer mixture having a smooth surface and / or having a continuous bubble content of at least 20% by volume, a crosslinked gel content of at most 10%, a minimum cross-sectional area of at least 1000 mm ² and a density of 250 kg / m ³ or less. The polymer mixture is a substantially random air polymerized with vinyl or vinylidene aromatic monomers and / or sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers (1) and one or more ethylene and C _3-20 aliphatic α-olefins (2). Olefin polymers (B) based on coalescing (A) and at least one ethylene, C _3-20 aliphatic α-olefins, and C _3-20 aliphatic α-olefins containing polar groups. The olefin polymer (B) does not include the vinyl or vinylidene aromatic monomers found in component (A).

Description

Olefin polymers and alpha-olefin / vinyl or alpha-olefin / vinylidene interpolymer blend foams

The present invention generally relates to polymeric foams based on mixtures of olefinic polymers with one or more α-olefin / vinyl monomer interpolymers and α-olefin / vinylidene monomer interpolymers. Vinyl and vinylidene monomers can be aromatic, sterically hindered aliphatic, or cycloaliphatic. The present invention relates in particular to continuous foam polymer foams based on such mixtures, in particular such foams are flexible and preferably low in density. The present invention also more preferably has a low density polymer foam (continuous foam or independent foam) based on a mixture having improved functionality compared to foams made only of olefinic polymers, with a smooth surface and a good appearance. Type). Such foams preferably have little crosslinking as is evident in the low insoluble gel content.

Various thermoplastic polymers can be used to make polymer foams. Certain thermoplastic polymers provide structures having a variety of useful properties and dimensions more easily than others. For example, polystyrene is an amorphous polymer that foams over a relatively wide range of temperatures to form foams having a wide range of continuous bubble contents. Semi-crystalline polymers, on the other hand, are typically foamed over a narrow temperature range (narrower than polystyrene) with typically a sharp drop in viscosity and melt strength as the temperature exceeds their crystalline melting point. This results in a foam which is largely free-formed. One method of broadening the temperature range and improving the range of processing properties by increasing the melt strength of the semicrystalline polymer includes the step of lightly crosslinking the polymer by peroxides, irradiation or other conventional means. Nevertheless, the resulting foams are usually overwhelmingly free cell (less than 20% by volume of continuous bubble content).

Uncrosslinked low density olefinic polymer foams typically have a rough surface in their manufacture. As the foam ages, the surface roughness of the foam may increase due to shrinkage or expansion of the foam. Rough surfaces are aesthetically undesirable for many applications (eg cushion packaging). In this case, these rough surfaces can be removed during the final foam production and become waste.

PCT publication WO / 98910015 describes mixtures of polyolefins and α-olefin / vinylidene monomer interpolymers. Examples 26, 27 and Examples 29-31 relate to foam materials made from such mixtures. Example 26 relates to a foam material having a width of 32 mm and a thickness of 15 to 17 mm. Example 27 relates to a material having a width of 34.5 mm and a thickness of 19 mm. Examples 29 to 31 show examples of the preparation of free-foamed foams (less than 20% continuous bubble content), but do not mention foam sizes.

Summary of the Invention

One embodiment of the invention is a polymer foam having a crosslinked gel content of 10% or less (preferably a minimum cross-sectional area of at least 1000 mm ² ) and a density of 250 kg / m ³ or less, wherein at least 70% by weight of the polymer in the foam this,

(A) (1) at least one vinyl or vinylidene aromatic monomer (a), at least one steric hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer (b) or at least one aromatic vinyl or vinylidene monomer and at least one steric hindered 8 to 65 mole% of monomer units derived from mixture (c) of aliphatic or cycloaliphatic vinyl or vinylidene monomers, and

(2) 35 to 92 mole percent of monomer units derived from ethylene, aliphatic α-olefins having 3 to 20 carbon atoms or mixtures thereof,

At least 80 mol% of monomer units derived from component (1) and component (2), a melt flow rate of 0.05 to 1000 g / 10 minutes and a crystalline melting point (T _m ) or glass transition temperature (T _g ) of about 80 ° C. or less 5 to 60% by weight of the above random random interpolymer and

(B) contains no monomer units derived from component (1) (a), component (1) (b) or component (1) (c), and contains ethylene, aliphatic α-olefins having 3 to 20 carbon atoms and polarity; A mixture of 95-40% by weight of at least one polymer having at least 80 mol% of monomer units derived from monomers selected from aliphatic α-olefins containing 3 to 20 carbon atoms containing a group [content of component (A) and component (B) The mixture, ie based on the total weight of components (A) and (B)].

The mixture may contain other polymerizable monomers and the foam may contain one or more conventional foaming accelerators, additives or both. In addition, the foam has a continuous bubble content of 20% by volume or more based on the total foamed volume. It is not necessary to use crosslinking to increase the polymer melt strength, add fillers (such as carbon black) to break the bubble walls, or mechanically break the bubble walls to achieve the desired continuous bubble content.

The glass transition temperature (T _g ) and crystalline melting point (T _m ) of component (A) or component (B) are integrated using a differential scanning calorimeter (DSC). The following procedure is used for DSC integration: Sample is melted completely by rapid heating to 180 ° C. and held at 180 ° C. for 4 minutes, cooled to about 40 ° C. below the predicted T _g at 10 ° C./min, and at this temperature. DSC sterilization at 4 minutes and heated to 150 ° C. at 10 ° C./min. T _m is obtained from the melting curve and is the peak melting temperature of the melting curve. T _g is obtained from the DSC melting curve using the half-height method (also called second heating).

The present invention relates to an extrusion foaming method for producing the polymer foam. The method comprises the steps of converting the mixture into a polymer melt (I); Introducing at least one blowing agent in the polymer melt at elevated pressure in a total amount of 0.2-5.0 g-mol per kg of polymer contained in the polymer melt to form a moldable gel; Cooling the moldable gel to an optimum temperature (III); And extruding the moldable gel from step (III) through the die into the low pressure region to form a foam.

Reference herein is made to the Periodic Table of the Elements, published in 1989 by CRC Press, Inc. regarding elements or metals belonging to a particular group. Reference to the feature group (s) is made for the particular group as reflected in the Periodic Table of Elements using the IUPAC system for numbering the particular group (s).

Unless stated otherwise, all ranges include the upper and lower limits and all numbers therebetween.

"Hydrocarbyl" means any aliphatic, cycloaliphatic, aromatic, aryl substituted aliphatic, aryl substituted alicyclic, aliphatic substituted aromatic or aliphatic substituted alicyclic group. "Hydrocarbyloxy" means a hydrocarbyl group having an oxygen bond incorporated therein and a carbon atom bonded thereto. An "aliphatic" compound means a compound in which the accumulation of carbon atoms is straight or branched.

"Copolymer" means a polymer in which monomer units derived from two different monomers are polymerized.

"Interpolymer" means a polymer in which monomer units derived from two or more different monomers are polymerized. These include copolymers, terpolymers and quaternary copolymers. "Monomer unit" means a polymer backbone portion derived from a single monomer.

"Continuous bubble foam" means a foam having a continuous bubble content of at least 20% by volume in accordance with ASTM D2856-94. By "soft foam" is meant a foam having an Asker C hardness of less than 80, preferably less than 70 and more preferably less than 60 in foams of density up to 250 kg / m ³ .

Ingredient (A)

The "substantial random interpolymer" (SRIP) of the present invention has a monomer distribution that can be described by Bernoulli statistical models or first or second Markovian statistical models as described in the literature [ See: JC Randall in POLYMER SEQUENCE DETERMINATION, Carbon-13 NMR Method, Academic Press New York, 1977, pp. 71-78]. Preferred SRIPs have a vinyl aromatic monomer distribution such that up to 15% of the total vinyl aromatic monomer content is present in a block of vinyl aromatic monomers of more than three units. More preferably, the interpolymer does not exhibit high isotacticity or syndiotacticity. This means that, in its carbon-13 nuclear magnetic resonance (C ¹³ -NMR) spectrum, methine carbon exhibits a meso double line arrangement or a racemic double line arrangement in which SRIP does not exceed 75% of the total peak region of the main chain methylene and methine carbons; It is meant to have a peak region corresponding to the backbone methylene.

The SRIP present in the foam of the present invention as part of component (A) comprises at least one ethylene and C _3-20 aliphatic α-olefin monomer (i), at least one vinyl or vinylidene aromatic monomer and sterically hindered aliphatic or cycloaliphatic vinyl Or vinylidene monomer (ii) and optionally up to 20 mole% of polymerizable ethylenically unsaturated monomer (iii) other than components (i) and (ii). The interpolymer has at least 80 mol%, preferably at least 90 mol%, more preferably 100 mol% of monomer units derived from components (i) and (ii).

Suitable α-olefins are aliphatic α-olefins having 3 to 20 (C _3-20 ), preferably 3 to 12 (C _3-12 ), more preferably 3 to 8 (C _3-8 ). As used herein, the subscript represents the number of carbon (C) atoms contained in the monomer, for example. Particularly suitable α-olefins are ethylene, propylene, butene-1, 4-methyl-1-pentene, hexene-1 or octene-1, and ethylene and propylene, butene-1, 4-methyl-1-pentene, hexene-1 And octene-1. Other optional polymerizable ethylenically unsaturated comonomers include norbornene and C _1-10 alkyl or C _6-10 aryl substituted norbornene, such as ethylene / styrene / norbornene interpolymers.

Suitable vinyl or vinylidene aromatic monomers for use in component (A) include compounds of the formula

In Formula 1 above,

R ¹ is selected from hydrogen and lower (C _1-4 ) alkyl radicals, preferably hydrogen or methyl,

Each R ² is independently selected from hydrogen and a C _1-4 radical, preferably hydrogen or methyl,

Ar is a phenyl group or a phenyl group mono- or missubstituted with a substituent or moiety selected from halogen (or halo-), C _1-4 alkyl and C _1-4 haloalkyl,

n is an integer of 0-4, Preferably it is an integer of 0-2, More preferably, it is 0.

Examples of vinyl aromatic monomers include styrene, vinyl toluene, α-methylstyrene, t-butyl styrene, chlorostyrene, and isomers thereof. Particularly suitable vinyl aromatic monomers include styrene and derivatives thereof substituted with lower alkyl (C _1-4 ) or halogens such as chlorine or bromine. Preferred monomers include styrene, α-methyl styrene, lower alkyl or phenyl ring substituted styrene derivatives such as ortho-, meta- and para-methylstyrene, ring halogenated styrenes, para-vinyl toluene or mixtures thereof. More preferred vinyl aromatic monomer is styrene.

A "sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compound" is an addition polymerizable vinyl or vinylidene monomer of the formula:

In Formula 2 above,

A ¹ is a C _6-20 cyclic aliphatic group, tert-butyl, or a substituted or unsubstituted norbornyl group,

R ³ is hydrogen or a C _1-4 alkyl group, preferably hydrogen or methyl,

Each R ⁴ is independently hydrogen or a C _1-4 alkyl group, preferably hydrogen or methyl,

R ³ and A ¹ together form a ring system.

Preferred aliphatic or cycloaliphatic vinyl or vinylidene compounds include monomers in which one of the carbon atoms containing ethylenically unsaturated bonds is tertiary or quaternary substituted. Examples of suitable A ¹ substituents include cyclohexyl, cyclohexenyl and cyclooctenyl. More preferred compounds include various isomeric vinyl-ring substituted derivatives of cyclohexene and substituted cyclohexene, and 5-ethylidene-2-norbornene. Particularly suitable compounds include 1-, 3- and 4-vinylcyclohexene.

SRIP preparation is the presence of one or more metallocenes or defined geometry catalysts and various cocatalysts, as described in two documents, which are incorporated herein by reference in their entirety: EP-A 0,416,815 and US Pat. No. 5,703,187. And a method of polymerizing a mixture of polymerizable monomers under. Preferred polymerization conditions include a pressure range of up to 3000 atmospheres (304 MPa) and a temperature range of -30 to 200 ° C. If the polymerization is carried out at temperatures above the monomer autopolymerization temperature of the individual monomers and the unreacted monomers are recovered, some monomers may be converted into their respective homopolymers by mechanisms such as free radical polymerization.

Examples of suitable catalysts and process conditions for preparing SRIP are described in U.S. Patent Application Nos. 702,475 (EP-A 514,828) and U.S. Patents 5,055,438, 5,057,475, 5,096,867, filed May 20, 1991. 5,064,802, 5,132,380, 5,189,192, 5,321,106, 5,347,024, 5,350,723, 5,374,696, 5,399,635, 5,470,993, 5,703,187 and 5,721,185. And patent applications are all incorporated herein by reference.

The preparation of the SPIP is suitably made at a temperature of -30 to 250C in the presence of the catalyst of formula (3).

In Formula 3 above,

Each C p ¹ is, independently, a substituted cyclopentadienyl group p-linked to M,

E is C or Si,

M is a Group 4 metal, preferably Zr or Hf most preferably Zr,

R ⁵ is each independently H or hydrocarbyl, silahydrocarbyl or hydrocarbylsilyl having 30 or less, preferably 1 to 20, more preferably 1 to 10, atoms of carbon (C) or silicon (S) ,

R ⁶ is each independently H or halo, H or carbon (C) or silicon (S) atom number of 30 or less, preferably 1 to 20, more preferably 1 to 10 hydrocarbyl, hydrocarbyloxy, Silahydrocarbyl, hydrocarbylsilyl,

Two R ⁶ groups together may form a C _1-10 hydrocarbyl substituted 1,3-butadiene,

m is 1 or 2.

Optionally, but preferably, the polymerization is carried out in the presence of an activating promoter. Particularly suitable substituted cyclopentadienyl groups include compounds of the formula

In Formula 4 above,

R ⁷ is each independently H or a hydrocarbyl, silahydrocarbyl or hydrocarbylsilyl having 30 or less carbon atoms, preferably 1 to 20, more preferably 1 to 10 atoms of carbon (C) or silicon (S); ,

Two R ⁷ groups may form a divalent derivative of a sulfo group.

Preferably, each R ⁷ is independently (including all isomers) hydrogen (H), methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenyl or silyl or (optionally) two The R ⁷ groups join together to form a fused ring system such as indenyl, fluorenyl, tetrahydroindenyl, tetrahydrofluorenyl or octahydrofluorenyl.

Particularly preferred catalysts are, for example, racemic- (dimethylsilandiyl) -bis- (2-methyl-4-phenylindenyl) zirconium dichloride, racemic- (dimethylsilandiyl) -bis- (2 -Methyl-4-phenylindenyl) zirconium 1,4-diphenyl-1,3-butadiene, racemic- (dimethylsilanediyl) -bis- (2-methyl-4-phenylindenyl-zirconium di-C _1-4 alkyl, racemic- (dimethylsilanediyl) -bis (2-methyl-4-phenylindenyl) zirconium di-C _1-4 alkoxide, or mixtures thereof.

Suitable limited geometry titanium based catalysts are selected from [N- (1,1-dimethylethyl) -1,1-dimethyl-1-[(1,2,3,4,5-h) -1,5,6, 7-tetrahydro-s-indasen-1-yl] silaneaminato (2-)-N] titanium dimethyl; (1-indenyl) (tert-butylamido) dimethyl-silane titanium dimethyl; ((3-tert-butyl (1,2,3,4,5-h) -1-indenyl) (tert-butylamido) dimethylsilane titanium dimethyl; and ((3-isopropyl) (1 , 2,3,4,5-h) -1-indenyl) (tert-butylamido) dimethylsilane titanium dimethyl, or mixtures thereof.

Other methods of making interpolymers suitable for use in the present invention have been described in various literatures. Longo and Grassi and Danielo, Longo and Grassi, Makromol. Chem., Volume 191, pages 2387 to 2396 (1990); D'Anniello et al., Journal of Applied Polymer Science, Volume 58, pages 1701-1706 (1995), describe a catalyst system based on methylalumoxane (MAO) and cyclopentadienyl-titanium trichloride (CpTiCl ₃ ). A method for producing ethylene-styrene copolymers using is reported. Xu and Lin, Xu and Lin, Polmer Preprints, Am. hem. Soc., Div. Polym. Chem., Volume 35, pages 686,687 (1994), reported a method for providing a random copolymer of styrene and propylene using a MgCl ₂ / TiCl ₄ / NdCl ₃ / Al (iBu) ₃ catalyst. In Lu et al., Jounal of Applied Polymer Science, Volume 53, pages 1453 to 1460 (1994), TiCl ₄ / NdCl ₃ / MgCl ₂ / Al (Et) ₃ catalysts are used for ethylene and styrene. A method of copolymerization is described. Simets and Mullut, Semetz and Mulhaupt, Macromol. Chem. Phys., V. 197, pp. 1071-1083, 1997 describe the effect of polymerization conditions on the copolymerization of styrene with ethylene using MeSi (Me ₄ Cp) (N-tert-butyl) TiCl _2- / methylaluminoxane Ziegler-Natta catalysts. have. Arai, Toshiaki and Suzuki, Arai, Toshiaki and Suzuki, Polymer Preprints, Am. Chem. Soc., Div. Polym. Chem., Volume 38, pages 349,350 (1997) and US Pat. No. 5,652,315 describe ethylene and styrene copolymers prepared using bridged metallocene catalysts. Methods of preparing alpha-olefin / vinyl aromatic monomer interpolymers such as propylene / styrene and butene / styrene are described in US Pat. No. 5,244,996 or 5,652,315 or in DE 197 11 339 A1. All of the above described methods for preparing interpolymer components are incorporated herein by reference. In addition, despite high isotacticity and not being "substantially random," Toru Aria et al., Polymer Preprints Vol, 39, No. 1, March 1998] Random copolymers of ethylene and styrene can also be used as mixed components in the manufacture of the foams of the invention.

SRIP can also be prepared by the method described in JP 07/278230 using the compound of formula 5

In Formula 5 above,

Cp ² and Cp ³ are each independently a cyclopentadienyl group, indenyl group, fluorenyl group, or a substituent thereof,

R ⁸ and R ⁹ are each independently H atom, halogen atom, C _1-12 hydrocarbon group, alkoxy group or aryloxyl group,

M is a group 4 group, preferably zirconium (Zr) or hafnium (Hf), most preferably Zr,

R ¹⁰ is an alkylene group or silandiyl group used to crosslink Cp ² and Cp ³ .

SRIP is also disclosed in WO 95/32095; WO 94/00500; And in Plastics Technology, p. 25 (1992.09), all of which are incorporated herein by reference in their entirety. At least one alpha-olefin / vinyl aromatic / vinyl aromatic / alpha-olefin tetrad as described in US Patent Application Serial No. 08 / 708,869, filed Sep. 4, 1996 and WO 98/09999.

An amount of atactic vinyl aromatic homopolymer can be prepared in the production of SRIP. This typically has little adverse effect on the present invention and can be tolerated. In some cases, the homopolymer may be separated from the desired interpolymer by conventional techniques. For the purposes of the present invention, the amount of atactic vinyl aromatic homopolymer is preferably less than 30% by weight, more preferably less than 20% by weight, based on the total weight of the interpolymer and the atactic vinyl aromatic homopolymer. .

SRIP can be modified by conventional methods such as grafting, hydrogenation and functionalization (eg sulfonation or chlorination).

The vinyl or vinylidene aromatic monomer and / or sterically hindered aliphatic or cycloaliphatic monomer content (1) in SRIP is preferably from 8 to 65 mol%, more preferably from 15 to 65 mol%. The interpolymer also preferably has an ethylene and / or C _3-20 aliphatic alpha-olefin content (2) of 35 to 92 mol%, more preferably 35 to 85 mol, especially when producing foams with smooth surfaces. %to be. This mole% is based on the sum of the moles of content (1) and content (2), in which case the total is 100 mole%.

Melt flow rate (I ₂ ) of SRIP (component A) is preferably 0.05 to 1000 g as accumulated according to ASTM (American Society for Testing and Materials) Test D1238, 190 ° C./2.16 kg weight). / 10min, more preferably 0.1 to 100g / 10min, even more preferably 0.2 to 50g / 10min. Further, the molecular weight distribution (weight average molecular weight / number average molecular weight (M _w / M _n ) or MWD) is 1.5 to 20, more preferably 1.8 to 10, even more preferably 2 to 5.

Ingredient (B)

Olefinic polymers suitable for use as the mixture component (B) contain no monomer units derived from vinyl or vinylidene aromatic monomers or sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and are not ethylene, unsubstituted. At least 80 mole%, preferably based on the total moles of monomer units, of monomer units derived from at least 1 mole% of monomers selected from C _3-20 aliphatic alpha-olefins, or aliphatic C _3-20 alpha-olefins containing polar groups Preferably at least 90 mol%, more preferably 100 mol%. The olefinic polymer may be a homopolymer, copolymer or interpolymer. Suitable polar group-containing aliphatic alpha-olefin monomers are, for example, ethylenically unsaturated nitriles (eg acrylonitrile, methacrylonitrile or ethacrylonitrile), ethylenically unsaturated anhydrides (eg maleic anhydride), ethylene Unsaturated unsaturated amides (e.g. acrylamide or methacrylamide), ethylenically unsaturated carboxylic acids (both monofunctional or difunctional) (e.g. acrylic or methacrylic acid), esters of ethylenically unsaturated carboxylic acids (especially lower, eg For example, C _1-6 alkyl esters) (e.g. methyl methacrylate, ethyl acrylate, hydroxyethyl-acrylate, n-butyl acrylate or methacrylate, or 2-ethyl-hexyl acrylate), ethylene Systemically unsaturated dicarboxylic acid imides such as N-alkyl maleimide, or N-aryl maleimide such as N-phenyl maleimide. Preferred polar group containing monomers include acrylic acid, vinyl acetate, maleic anhydride and acrylonitrile. The olefinic polymer may contain a halogen such as fluorine, chlorine or bromine. Preferred halogen-containing olefinic polymers include chlorinated polyethylene (CPE). Preferred olefinic polymers include homopolymers or interpolymers of ethylene or aliphatic (including alicyclic) C _2-18 alpha-olefins. Examples of such preferred polymers are homopolymers of ethylene or propylene, and interpolymers of two or more C _2-18 alpha-olefin monomers. Other preferred olefinic polymers include interpolymers of ethylene with one or more other C _3-8 alpha-olefins such as 1-butene, 4-methyl-1-pentene, 1-hexene or 1-octene.

While it may be desirable to be substantially free of crosslinking, conventional means of lightly crosslinking the polymer in both component (A) and component (B) may be used to maintain thermoplastics while increasing shear thinning of the polymer. Such means include, for example, the use of coupling agents such as, but not limited to, radiation, azide or peroxides. The degree of crosslinking can increase the polymer melt strength which improves one or more of the foaming capacity, interfacial strength and mechanical properties. Examples of polymers modified in this way are high melt strength PPs such as Profax ^™ PF814 (manufactured by Montel) and DaFlo ^™ 130D (manufactured by Borealis).

As used herein, "coupling agent" means a compound or mixture thereof, optionally used to couple or optionally foam the polymer or polymer mixture. Typical coupling compounds are multifunctional and insertions can occur at their C-H bonds. Such multifunctional compounds have two or more, preferably two, functional groups in which a C-H insertion reaction can occur.

Suitable coupling agents include, but are not limited to, peroxides, silanes, sulfur, radiation or azide based curing systems. All descriptions of the various crosslinking techniques are described in US Patent Application Nos. 08 / 921,641 and 08 / 921,642, both of which are filed on August 27, 1997 and incorporated herein by reference in their entirety. . Dual curing systems using a combination of heat, humidification curing and radiation steps can be used effectively. Dual curing systems are described and claimed in US Patent Application No. 536,022, filed September 29, 1995, which is incorporated herein by reference. For example, using a peroxide coupling agent with a silane coupling agent, using a peroxide coupling agent with radiation, using a sulfur containing coupling agent with a silane coupling agent, etc. are preferable.

Multifunctional compounds that can be inserted at CH bonds also include carbene forming compounds such as salts of alkyl and aryl hydrazones and diazo compounds, and alkyl and aryl azides (RN ₃ ), acyl azides (RC (O)). N ₃ ), azidoformate (ROC (O) -N ₃ ) [e.g. tetramethylene bis (azido-formate) (see US Pat. No. 3,284,421), sulfonyl azide (R-SO _2- N ₃ ), phosphoryl azide ((R)) _2- (PO) -N ₃ ), phosphinic acid azide (R ₂ -P (O) -N ₃ ) and silyl azide (R ₃ -Si-N Nitrate-forming compounds such as ₃ ).

Poly (sulfonyl azide) is any compound having at least two reactive sulfonyl azide groups (—SO ₂ N ₃ ). Preferred poly (sulfonyl azide) is a structure of formula XRX wherein X is each SO ₂ N ₃ , and R is an unsubstituted or inertly substituted hydrocarbyl, hydrocarbyl ether or silicon containing group, SRIP and sulf Sufficient carbon, oxygen, or silicon, preferably carbon atoms, enough, more preferably one or more, even more preferably enough to separate the sulfonyl azide groups to facilitate the reaction between the polyvinyl azide Has at least two, most preferably at least three carbon, oxygen or silicon, preferably carbon atoms, between functional groups.

"Inertly substituted" refers to being substituted with atoms or groups that do not inappropriately interfere with the desired reaction (s) or desirable properties of the resulting crosslinked polymer. Such groups include fluorine, aliphatic or aromatic ethers, siloxanes, as well as sulfonyl azide groups when more than two SRIP chains are joined. R in a suitable structure includes aryl, alkyl, aryl alkaryl, arylalkyl silanes or heterocyclic groups, or other groups that separate and separate insulative sulfonyl azide groups as described above. More preferably, R comprises at least one aryl group between sulfonyl groups, most preferably at least two aryl groups (R is 4,4'-diphenylether or 4,4'-biphenyl) It includes. When R is one aryl group, the group is preferably more than one ring as in the case of naphthylene bis (sulfonyl azide). Poly (sulfonyl) azides are such compounds as 1,5-pentane bis (sulfonyl azide), 1,8-octane bis (sulfonyl azide), 1,10-decane bis (sulfonyl azide), 1 , 10-octadecane bis (sulfonyl azide), 1-octyl-2,4,6-benzene tris (sulfonylazide), 4,4'-diphenyl ether bis (sulfonyl azide), 1,6 -Bis (4'-sulfonazidophenyl) hexane, 2,7-naphthalene bis (sulfonyl azide), and chlorinated aliphatic hydrocarbons having an average chlorine number of 1 to 8 and a sulfonyl azide group number of 2 to 5 per molecule Mixed sulfonyl azide, and mixtures thereof. Preferred poly (sulfonyl azide) s are oxy-bis (4-sulfonylazidobenzene), 2,7-naphthalene bis (sulfonyl azido), 4,4'-bis (sulfonyl azido) biphenyl, 4 , 4'-diphenyl ether bis (sulfonyl azide) and bis (4-sulfonyl aziphenyl) methane, and mixtures thereof.

The poly (sulfonyl azide) and polymer or mixture to be coupled are mixed at a first temperature above the melting point of the lowest melting point component in the mixture, and after mixing, a second temperature higher than the first temperature, typically above 100 ° C. More frequently, the reaction is heated at a temperature exceeding 150 ° C. The preferred temperature range depends on the nature of the azide used.

For coupling, the sulfonyl azide is mixed with the polymer and heated to a temperature above the decomposition temperature of the sulfonyl azide. "Decomposition temperature" refers to the temperature at which azide is converted to its corresponding sulfonyl nitrite while removing nitrogen and heat in the process as accumulated by differential scanning calorimetry (DSC).

Other suitable coupling agents include phenol, aldehyde-amine reaction products, substituted ureas, substituted guanidines, substituted xanthates, substituted dithiocarbamates, sulfur containing compounds such as thiazoles, imidazoles, sulfenamides, thiurami Disulfide, paraquinonedioxime, dibenzoparaquinonedioxime, sulfur) and mixtures thereof. See Encyclopedia of Chemical Technology, Vol. 17, 2nd edition, Interscience Publishers, 1968; and Organic Peroxides, Daniel Seem, Vol. 1, Wiley-Interscience, 1970].

Suitable peroxides include aromatic diacyl peroxides, aliphatic diacyl peroxides, dibasic acid peroxides, ketone peroxides, alkyl peroxyesters, alkyl hydroperoxides (eg diacetyl peroxides), dibenzoylperoxides; Bis-2,4-dichlorobenzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butylperbenzoate, tert-butyl cumyl peroxide, 2,5-bis (tert-butyl Peroxy) -2,5-dimethylhexane, 2,5-bis (tert-butylperoxy) -2,5-dimethylhexylene-3; 4,4,4 ', 4'-tetra- (tert-butylperoxy) -2,2-dicyclohexylpropane, 1,4-bis- (tert-butylperoxyisopropyl) -benzene, 1 , 1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, lauroyl peroxide, succinic peroxide, cyclohexanone peroxide, tert-butyl peracetate and butyl hydroper Oxides.

Suitable phenols are described in US Pat. No. 4,311,628, the disclosure of which is incorporated herein by reference. One example of a phenolic curing agent is a condensation product of a halogen substituted phenol or a C _1-10 alkyl substituted phenol with an aldehyde or a bifunctional phenoldialcohol in an alkaline medium.

Suitable aldehyde-amine reaction products include formaldehyde-ammonia; Formaldehyde-ethylchloride-ammonia; Acetaldehyde-ammonia; Formaldehyde-aniline; Butylaldehyde-aniline; And heptaaldehyde-aniline.

Suitable substituted ureas include trimethylthiourea; Diethylthiourea; Dibutylthiourea; Triphenylthiourea, 1,3-bis (2-benzothiazolylmercaptomethyl) urea; And N, N-diphenylthiourea.

Suitable substituted guanidines include diphenylguanidine; Di-o-tolylguanidine; Diphenylguanidine phthalate; And di-o-tolylguanidine salts of dicatechol borate.

Suitable substituted xanthates include zinc ethyl xanthate, sodium isopropyl xanthate, butyl xanthate disulfide, potassium isopropyl xanthate, and zinc butyl xanthate.

Suitable dithiocarbamates include copper dimethyl-, zinc dimethyl-, tellurium diethyl-, cadmium dicyclohexyl-, lead dimethyl-, lead dimethyl-, selenium dibutyl-, zinc pentamethylene-, zinc didecyl-, and Zinc isopropyloctyl-dithiocarbamate.

Suitable thiazoles include 2-mercaptobenzothiazole, zinc mercaptothiazolyl mercaptide, 2-benzothiazolyl-N, N-diethylthiocarbamyl sulfide, and 2,2-dithiobis (benzothiazole) do.

Suitable imidazoles include 2-mercaptoimidazoline and 2-mercapto-4,4,6-trimethyldihydropyrimidine.

Suitable sulfenamides are N-tert-2-benzothiazole-, N-cyclohexylbenzothiazole-, N, N-diisopropylbenzothiazole-, N- (2,6-dimethylmorpholino)- 2-benzothiazole-, and N, N-diethylbenzothiazole-sulfenamide.

Suitable thiurami disulfides are N, N'-diethyl-, tetrabutyl-, N, N'-diisopropyldioctyl-, tetramethyl-, N, N'-dicyclohexyl-, and N, N'- Tetralauryl-thiuramidisulfide.

Alternatively, silane coupling agents may be used. In this regard, any silane capable of effectively grafting the polymers of the invention can be used. Suitable silanes are ethylenically unsaturated hydrocarbyl groups (e.g. vinyl, allyl, isopropenyl, butenyl, cyclohexenyl or γ- (meth) acryloxy allyl groups) and hydrolyzable groups (e.g. hydrocarbyloxy, hydro Unsaturated silanes including carbonyloxy or hydrocarbylamino groups). Examples of hydrolyzable groups include methoxy, ethoxy, formyloxy, acetoxy, propionyloxy and alkyl or arylamino groups. Preferred silanes include unsaturated alkoxy silanes that can be grafted to the polymer. These silanes and their preparation are described more fully in US Pat. No. 5,266,627, the teachings of which are incorporated herein by reference. Vinyl trimethoxy silane (VTMOS), vinyl triethoxy silane, γ- (meth) acryloxy propyl trimethoxy silane and mixtures of these silanes are preferred silane coupling agents for use in the present invention.

Olefinic polymers also contain up to 20 mole percent of monomer units based on other nonaromatic interpolymerizable monomers, such as C _4-20 dienes, preferably butadiene or 5-ethyldiene-2-norbornene. can do. Olefinic polymers are further characterized by their long or short chain branching (LCB or SCB) and their distribution.

Olefin-based polymers such as conventional LCB low density polyethylene (LDPE) can be prepared by high pressure polymerization using free radical initiators. When used in the compositions of the present invention, LDPE typically has a density (ρ) of less than 0.94 g / cc (ASTM D 792) and a melt flow rate (I ₂ ) of 0.01 to 100 g / 10 min, preferably 0.1 to 50 g / 10 min. (ASTM test D 1238, condition I).

Olefinic polymers that do not contain LCB, such as linear low density polyethylene polymers (heterogeneous LLDPE) or linear high density polyethylene polymers (HDPE), are typically produced from Ziegler polymerization reactions. U.S. Patent 4,076,698 describes this process. These olefinic polymers may be referred to as "heterogeneous polymers".

HDPE used in the present invention usually consists mainly of linear polyethylene long chains. HDPE has a ρ (ASTM-D1505) of at least 0.94 g / cc and an I ₂ (ASTM-1238, condition I) of 0.01 to 100 g / 10 min, preferably 0.1 to 50 g / 10 min.

Heterogeneous LLDPE generally has a p (ASTM-D792) of 0.85 to 0.94 g / cc or more and an I ₂ (ASTM-1238, condition I) of 0.01 to 100 g / 10 min, preferably 0.1 to 50 g / 10 min. The LLDPE is preferably a polymerized _mixture of ethylene and one or more C _3-18 , more preferably C _3-8 α-olefins. Preferred α-olefins include 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene.

Other suitable olefinic polymers include polymers or homogeneous polymers, usually referred to as uniformly branched, one example of which is homogeneous LLDPE. Homogeneous polymers do not contain LCB at all and have only side chains derived from monomers (if they have two or more carbon atoms). Homogeneous polymers are those prepared as described in US Pat. No. 3,645,99 and those made using a so-called single-site catalyst in batch reactors with relatively high olefin concentrations (described in US Pat. Nos. 5,026,798 and 5,055,438). Things). Homogeneously branched homogeneous polymers typically have a random comonomer distribution within a given interpolymer molecule and similar ethylene / comonomer ratios between the interpolymer molecules.

Suitable homogeneous LLDPEs have a ρ (ASTM-D792) of 0.85 to 0.94 g / cc and I ₂ (ASTM-1238, condition I) of 0.01 to 100 g / 10 min, preferably 0.1 to 50 g / 10 min. The homogeneous LLDPE is preferably produced from the same monomers as the heterogeneous LLDPE.

Particularly suitable groups of olefinic polymers are often referred to as substantially linear ethylene / α-olefinic polymers or substantially linear ethylene polymers (collectively referred to as “SLEP”). SLEP has similar processability as LDPE and has similar strength and toughness as LLDPE. Like conventional homogeneous polymers, SLEP has a single melt peak, which contrasts with heterogeneous linear ethylene / a-olefin (EAO) interpolymers having two or more melt peaks polymerized with conventional Ziegler catalysts (melt peaks). Is integrated using a differential scanning calorimeter, ie DSC). US Pat. Nos. 5,272,236 and 5,278,272, which are incorporated herein by reference, describe SLEP and methods for their preparation.

Suitable SLEPs have a ρ (ASTM-D792) of 0.85 to 0.97 g / cc, preferably 0.85 to 0.955 g / cc, especially 0.855 to 0.92 g / cc and I ₂ (ASTM-1238, conditions 190 ° C./2.16 kg). 0.01 to 1000 g / 10 min, preferably 0.1 to 100 g / 10 min, in particular 0.01 to 10 g / 10 min.

Other suitable olefinic polymers are described in US patent application Ser. No. 09 / 359,486, filed July 22, 1999 and the corresponding PCT international application (WO 97/26287, published July 24, 1997). The teachings of which are incorporated herein by reference. These EAO interpolymers have an I ₂ greater than 1000 g / 10 min or an M _n less than 11,000.

SLEP may be a homopolymer of C _2-20 α-olefins such as ethylene, propylene or 4-methyl-1-pentene. It may also be an interpolymer of ethylene with one or more of C _3-20 α-olefins, C _2-10 acetylenically unsaturated monomers, or C _4-18 diolefins. SLEP interpolymers may also be polymerized one or more other unsaturated monomers.

Preferred polymers suitable for use as component (B) include LDPE, HDPE, heterogeneous and homogeneous LLDPE, SLEP, polypropylene (PP) [including isotactic polypropylene, syndiotactic and rubber cured polypropylene] or ethylene At least one of -propylene interpolymer (EP), chlorinated polymer (such as CPE), ethylene-vinyl acetate copolymer (EVA), and ethylene-acrylic acid copolymer (EAA). For EVA, EAA and CPE, I ₂ (ASTM-1238, conditions 190 ° C./2.16 kg) is usually 0.01 to 1000 g / 10 min, preferably 0.01 to 100 g / 10 min, in particular 0.01 to 10 g / 10 min. Satisfactory PP has a melt flow rate (MFR) (ASTM-1238, condition 230 ° C./2.16 kg) of 0.01 to 1000 g / 10 min, preferably 0.01 to 100 g / 10 min, in particular 0.01 to 10 g / 10 min.

Mixture composition

In the mixture of components (A) and (B), component (A) is at least 5% by weight, preferably at least 15% by weight, most preferably at least 20% by weight, preferably at most 60% by weight of the mixture. Even more preferably at most 55% by weight, most preferably at most 50% by weight. All percentages are based on the total weight of components (A) and (B). Thus, the preferred content of component (B) is equal to simply 100% by weight minus the amount of component (A).

If at least 60% by weight of component (A) is used in the polymer mixture, the resulting product will have a density of at least 250 kg / m ³ and the foam will disintegrate. If less than 5% by weight of component (A) is used in the polymer mixture, the continuous bubble content does not increase very much or the surface properties (ie smoothness) do not improve very much.

The mixtures of the present invention may be prepared by any suitable means known in the art, for example by dry mixing in pellet form at a desired ratio and then melt mixing in an apparatus such as a screw extruder or Banbury mixer. Dry mixed pellets can be melt processed directly to the final solid product, for example by injection molding. The mixture may also be prepared by direct polymerization without separating the mixture components. Direct polymerization can, for example, use one or more catalysts in one reactor or in two or more reactors connected in series or in parallel, and can change one or more of operating conditions, monomer mixtures and catalyst selection.

The polymer portion of the foam of the present invention may, if necessary, contain 30% by weight or less of polymers other than component (A) and component (B). However, the polymer portion of the foam preferably contains at least 70%, more preferably at least 90% and most preferably 100% by weight of components (A) and (B) based on the total weight of the polymer. Do.

In selecting the polymer mixture components, adjusting the viscosity of the polymer tends to improve mixing to minimize problems such as voids in the foam or bubbles formation on the foam surface. This also serves to improve foam properties.

The polymer mixture composition described above can be converted to the foam product using any conventional method. Foam products include, for example, thermoplastic polymer foams, extruded polymer strand foams, expandable thermoplastic foam beads, expanded thermoplastic foam beads or expanded and fused thermoplastic foam beads. The foam product can be converted to the product using any conventional process or method. For example, any one or more of the methods of inflation, coalescence, and bonding may be used to produce such articles, in particular from expandable foam beads. The foam product can take any known physical shape such as extruded sheets, rounds, rods, planks and profiles. The expandable beads can be molded into any known structure using foam products, including but not limited to the structures described above.

Conventional LDPE foam processes are considerably limited in terms of the temperature range in which suitable foams can be produced. This range is often below 1 ° C. The polymer mixture foams of the present invention range from 2 to 6 ° C. wider than this. This results in greater control in selecting foam properties such as continuous bubble content.

The polymeric foams of the present invention can be readily obtained from conventional foam manufacturing techniques. For example, conventional extrusion foaming processes are used to convert the polymer mixture components into a polymer melt and incorporate the foam into the polymer melt to form a moldable gel. The moldable gel is then extruded through a die to form the desired product. Depending on the die and operating conditions, the product may be transformed from the extruded foam planks or rods into foam beads through coalesced foam strand products, and then into cut strands of the ultimately moldable beads.

Before extruding the moldable gel through the die, the gel is typically cooled to optimum temperature. When the optimal temperature for the production of foam is higher than the polymer glass transition temperature (T _g) of the normal individual components, or having a sufficient degree of crystallinity has a melting point (T _m) in the vicinity of the T _m. "Near" refers to the temperature at which it is and a little higher or lower, and this temperature range depends mainly on the presence of a stable foam. The temperature is preferably ± 30 ° C of T _m . In the case of the foam of the present invention, the optimum foaming temperature is a category in which the foam does not disintegrate.

The blowing agent may be mixed or incorporated into the polymer melt by any means known in the art, such as by using an extruder, mixer or blender. The blowing agent is mixed with the polymer mixture at elevated pressures sufficient to prevent most of the molten polymer material from expanding and to allow the blowing agent to be homogeneously dispersed. Optionally, the nucleating agent may be mixed with the polymer melt or dry mixed with the polymer material and then plasticized or melted.

Component (A) and component (B) can be dry mixed and fed to the extruder hopper. With component (B) at least partially in the molten state, component (A) can also be added to the extruder. When added as such, component (A) may be part of a polymer concentrate that may include other additives or components, such as pigments.

To optimize the physical properties of the foam, the moldable gel is typically cooled to a lower temperature from a temperature that promotes melt mixing and then the gel is passed through a die. The gel is cooled in an extruder or other mixing device or in a separate cooler.

When producing extruded foam, extruded strand foam or foam beads, the cooled moldable gel is passed through a die of the desired form (a die with a suitable number of holes) to a reduced pressure or low pressure region to promote foaming. Is introduced. The low pressure region has a lower pressure than the pressure maintained before the moldable gel is extruded through the die. The low pressure may be above atmospheric pressure or below atmospheric pressure (vacuum), but atmospheric pressure is preferred.

The foam structure of the present invention can be formed in the form of coalesced strands by extruding the composition of the present invention through multiple orifice dies. Arrange the orifices such that adjacent streams of the melt extrudate are in contact with each other during the foaming process such that the contact surfaces are bonded to each other with a sufficient degree of adhesion to provide an integral foam structure. The molten extrudate stream exiting the die preferably takes the form of strands or profiles and is preferably foamed, coalesced, and adhered to each other to form an integral foam structure. Preferably, the individual strands or profiles incorporated maintain adhesion in the unitary structure to prevent the strands from leaving under the stresses encountered during the manufacture, molding and use of the foam. US Pat. Nos. 3,573,152 and 4,824,720, which are incorporated herein by reference, describe devices and methods used to make coalesced structures.

Foams of the present invention are also prepared using the cumulative extrusion process and apparatus shown in US Pat. Nos. 4,323,528 and 5,817,705, which are incorporated herein by reference. The apparatus, commonly known as "extruder-integrated system", performs the process intermittently rather than continuously. The apparatus includes a delay region or integrated apparatus in which the moldable gel is maintained under conditions such that foaming does not occur. The delay zone is equipped with a discharge die open in the low pressure zone (eg atmospheric pressure zone). The die preferably has an orifice that can be opened or closed by a gate external to the delay area. Operation of the gate has no effect on the composition except that the moldable composition flows through the die. Almost simultaneously with opening the gate, mechanical pressure is applied to the gel by a mechanism (such as a mechanical ram) to extrude the gel through the die into the low pressure region. This mechanical pressure is sufficient force to allow the moldable gel to pass through the die at a rate that is fast enough to prevent sufficient foaming from occurring inside the die and slow enough to prevent irregular cross-sectional areas or shapes from forming in the foam. In addition to this intermittent operation, the process and its process products are exactly as produced in a continuous extrusion process.

The foam structure of the present invention may also be molded into foam beads suitable for molding into articles by extrusion of pre-expanded beads containing blowing agents. The beads can be molded with expansion times to form various types of products. Methods of making expanded beads and molded expanded beam foam products are described in the literature. Plastic Foams, Part II, Frisch And Saunders. pp. 544-585, Marcel Dekker, Inc. (1973) and Plastic Materials, Brydson, 5th Ed., Pp. 426-429, Butterworths (1989).

Expandable beads and expanded beads can be produced batchwise or by an extrusion process. The batch production method of inflatable beads is similar to that of expandable polystyrene (EPS). The polymer mixture granules prepared by melt mixing or in-reactor mixing are impregnated with a blowing agent in an aqueous suspension or an anhydrous blowing agent in a pressurized vessel at elevated temperature and pressure. The granules are quickly released into the reduced pressure zone to expand the granules into foam beads or to cool and release the granules as unexpanded beads. In a separate step, the unexpanded beads are heated, for example, with steam or hot air. To expand them.

The extrusion method follows the conventional foam extrusion process described above for the die orifice. The die has a plurality of holes. To produce the unfoamed beads, the foamable strands exiting the die orifice are quenched directly in a cold water bath to prevent foaming and then the quenched strands are pelletized. Alternatively, the strands are cut into pellets or granules at the die surface and then expanded to convert the strands into foam beads.

The beads are then loaded by any means known in the art, for example, by loading the beads into a mold and compressing the mold to compress the beads, for example by heating the beads with steam to coalesce the beads. To form a product. Optionally, the beads may be impregnated with air or other blowing agent at elevated pressure and temperature and then loaded into the mold. In addition, the beads can be heated and then loaded. The foam beads can then be molded into blocks or shaped articles by suitable molding methods known in the art. Some of these methods are taught in US Pat. Nos. 3,504,069 and 3,953,558, which are incorporated herein by reference. C. P. Park, supra, p. 191, pp. 197-198, and pp. 227-229, which are incorporated herein by reference, teach well about the method and the molding method.

US Pat. Nos. 4,379,853 and 4,464,484, which are incorporated herein by reference, describe methods for making foam beads. When producing foam beads rather than foams, the mixture used to prepare the foams of the invention is first converted to discrete resin particles such as granulated resin pellets. These resin particles are suspended in a liquid medium in which they are substantially insoluble (eg water), and then a blowing agent is introduced into the liquid medium. The use of elevated temperature and elevated pressure in a pressurized vessel, such as an autoclave, facilitates impregnation of the particles with a blowing agent. The impregnated particles are released from the pressure vessel to the atmospheric or reduced pressure region and the particles are expanded into foam beads.

Expandable thermoplastic polymer beads can be easily obtained in a variation of the extrusion process described above. This variant involves cooling the foamable gel below the temperature at which foaming occurs (a) and extruding the cooled gel through a die having one or more orifices to form a corresponding plurality of essentially continuous expandable thermoplastic strands. (B) and pelletizing the expandable thermoplastic strand to form the expandable thermoplastic beads.

Any conventional blowing agent can be used to make the foams of the present invention. Such conventional blowing agents fall into three broad categories: inorganic blowing agents, organic blowing agents and chemical blowing agents. Suitable inorganic blowing agents include nitrogen, sulfur hexafluoride (SF ₆ ), argon, water, air and helium. Organic blowing agents include, but are not limited to, carbon dioxide (CO ₂ ), aliphatic C _1-9 hydrocarbons, aliphatic C _1-3 alcohols, and fully or partially halogenated aliphatic C _1-4 hydrocarbons. Aliphatic hydrocarbons include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane and the like. Aliphatic alcohols include methanol, ethanol, n-propanol and isopropanol. Fully and partially halogenated aliphatic hydrocarbons include fluorocarbons, chlorocarbons, and chlorofluorocarbons. Examples of fluorocarbons are methyl fluoride, perfluoromethane, ethyl fluoride, 1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161), 1,1,1-trifluoro Roethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1, 3,3-pentafluoropropane, pentafluoroethane (HFC-125), difluoromethane (HFC-32), perfluoroethane, 2,2-difluoropropane, 1,1,1-tri Fluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane. Partially halogenated chlorocarbons and chlorofluorocarbons for use in the present invention include methyl chloride, methylene chloride, ethyl chloride, 1,1,1-trichloroethane, 1,1-dichloro-1-fluoroethane (HCFC-141b ), 1-chloro-1,1-difluoroethane (HCFC-142b), chlorodifluoromethane (HCFC-22), 1,1-dichloro-2,2,2-trifluoroethane (HCFC- 123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). Fully halogenated chlorofluorocarbons include trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trichloro-trifluoroethane (CFC-113), dichlorodichloromethane (CFC -114), chloroheptafluoropropane and dichlorohexafluoropropane. Chemical blowing agents azodicarbonamide, azodiisobutyronitrile, benzene-sulfohydrazide, 4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonyl semi-carbazide, barium azodicarboxylate , N, N'-dimethyl-N, N'-dinitroso-terephthalamide, trihydrazino triazine, and mixtures of citric acid and sodium bicarbonate (e.g., Scheringer Ingelheim under the trade name Hydroserol ^™ ) Various products sold by the company. The aforementioned blowing agents can all be used alone or in combination with one or more other blowing agents.

The blowing agent or blowing agent mixture is present in an amount sufficient to convert the polymer melt to a foamable gel. It is preferably used in an amount of 0.2 to 5.0 g-mol, more preferably 0.5 to 3.0 g-mol and even more preferably 0.7 to 2.5 g-mol of blowing agent per kg of polymer present in the polymer melt.

Nucleating agents may be added to the polymer melt or foamable gel to control the foam bubble size. Preferred nucleating agents include inorganic materials such as calcium carbonate, talc, clay, silica, barium stearate, diatomaceous earth, and mixtures of citric acid and sodium bicarbonate. Other nucleating agents conventionally used to make polymeric foams can also be used. When a nucleating agent is formed, it is present in an amount greater than 0 and no greater than 5 parts per 100 parts by weight of polymer present in the polymer melt. This range is preferably greater than 0 and no more than 3 phr.

Various conventional additives may be incorporated into the foams of the present invention. Such additives include, but are not limited to, inorganic fillers, conductive fillers, pigments, antioxidants, acid scavengers, flame retardants, ultraviolet absorbers, processing aids, extrusion aids, permeability modifiers, antistatic agents and other thermoplastic polymers. Certain additives, such as inorganic and conductive fillers, may also act as nucleating agents, promote the formation of continuous bubbles, or both.

Permeable modifiers (or stability modifiers) may be added to the foams of the present invention to increase dimensional stability. Preferred formulations include amides and esters of C _10-24 fatty acids. US Pat. Nos. 3,644,230 and 4,214,054, which are incorporated herein by reference, describe such formulations. Monoesters also reduce static during or after foam production. Examples of preferred formulations include stearyl stearamide, glycerol monostearate, glycerol monobehenate and sorbitol monostearate. If present, such agents are used in amounts of greater than 0 and less than 10 phr based on the polymer in the foamable gel.

Perforating the foam of the present invention increases or promotes gas permeation exchange where the blowing agent exits the foam and air enters the foam. Perforated foam is preferably defined as having multiple channels regardless of the longitudinal expansion direction of the foam. The channels may pass partially through the foam from one surface of the foam or completely through the foam from one surface of the foam to the other outer surface. Such channels are preferably formed over substantially the entire outer foam surface and are preferably formed at even or nearly uniform intervals. Suitable spacing is 2.5 cm or less, preferably 1.3 cm or less. US Pat. Nos. 5,424,016, 5,585,058, WO 92/19439 and WO 97/22455, which are incorporated herein by reference, provide excellent information on perforation.

If necessary, the foam of the present invention is post-treated by any known means to increase the foam continuous bubble content. Such post-treatment methods include, but are not limited to, expanding the foam by mechanically compressing the foam and then exposing it to steam or hot air.

The foam of the present invention is excellent in dimensional stability. Preferred foams maintain at least 80% of their initial volume when measured one month after the initial volume measurement is made within 30 seconds of foam expansion. The volumetric measurement can use a suitable method such as volumetric displacement of water.

The foam of the present invention is substantially free of crosslinking as indicated by a crosslinked gel content of 10% or less based on the total weight of the foam or polymer (ASTM D-2765-84, Method A). The crosslinked gel content is preferably as low as possible and the foam properties are not adversely affected by trace amounts of crosslinking, such as naturally occurring crosslinks without the use of crosslinkers or radiation.

Ρ of the foam of the invention is less than 250 kg / m ³ , preferably less than 150 kg / m ³ , more preferably less than 100 kg / m ³ , even more preferably less than 80 kg / m ³ , most preferably 5 to 100 kg / m ³ (measured according to ASTM D3575-93, Appendix W, Method B). The average bubble size of the foam is from 0.05 to 10.0 mm, preferably from 0.1 to 5.0 mm, more preferably from 0.2 to 3.0 mm (ASTM D3576). The continuous bubble content of the foam is from 0.01 to 99.9% by volume, depending on the choice of components and the change in process conditions. Foams with a continuous bubble content of less than 20% by volume generally belong to the group known as free-foamed foams. Known as continuous foamed foams, the continuous foam content is typically at least 20% by volume, preferably at least 25% by volume and more preferably at least 30% by volume, based on the total volume of the foam. The continuous bubble content is 100% by volume or less, preferably 95% by volume or less, more preferably 90% by volume or less (ASTM D2856-94), based on the total volume of the foam.

The Asker-C hardness of the foam is 80 or less, preferably 70 or less, more preferably 60 or less. The hardness measurement of the foam uses an Asker C durometer for foamed rubber and yarns in accordance with ASTM D2240-97, but with a spherical indentation of 5 mm diameter.

The foam of the invention preferably has a minimum cross-sectional area of at least 1000 mm ² , preferably at least 1500 mm ² and most preferably at least 2000 mm ² . "Minimum cross-sectional area" refers to the minimum cross-sectional area of the foam. For example, the minimum cross-sectional area of a plank foam 50 mm wide x 20 mm thick x 3 m long is 1000 mm ² . In the case where the foam is sheet or plank, the thickness is at least 1 mm, preferably at least 3 mm, more preferably at least 5 mm, even more preferably at least 7 mm. The width is at least 50 mm, preferably at least 75 mm, more preferably at least 1000 mm. As used herein, the "thickness" of a foam plank or sheet refers to its minimum cross-sectional area (eg, the cross-sectional area measured from one plane to the opposite plane). If the foam is present in a circular or rod shape, the diameter is preferably at least 40 mm, preferably at least 50 mm, more preferably at least 75 mm.

The drop test optimum C-factor (ASTM-D1596) of the foam is 6 or less, preferably 5 or less, more preferably 4 or less.

The foams of the invention can now be used in all applications where foams of density and continuous or independent bubble content comparable to the foams of the invention are used. Such applications include cushioning packaging for finished electronic products such as computers, televisions and kitchenware (eg corner blocks, reinforcements, saddles, pouches, bags, bags, overlaps, slippers, capsules); Packaging or protective materials for explosive materials or devices; Object manipulation means (trays, carry boxes, box liners, carry box inserts and separators, shunts, cores, boards, partial spacers and partial separators); Workbench aids (Apron, table and bench covers, floor mats, seat cushions); Automobiles (shock absorbers in headliners, bumpers or doors, carpet support layers, sound insulation); Floats (eg lifejackets, vests and belts); Sporting and leisure items (eg athletic mats and bodyboards); Insulation (eg construction and building insulation); Sound insulation (eg construction and building sound insulation); Gaskets, grommet, sealants; Printing and typewriter winding materials; Display container inserts; Missile container padding; Military shell holders; Blocking and reinforcing materials of various kinds during transportation; Preservation and packaging materials; Automotive rattling pads, seals; Medical devices, skin contact pads; Cushioned pellets; And vibration separation pads. The above list merely illustrates a number of suitable applications. It will be apparent to those skilled in the art that further applications may be made without departing from the scope or spirit of the invention.

The following examples illustrate the invention, which does not limit the scope of the invention. Arabic numerals describe embodiments of the invention, and alphabetical letters indicate comparative examples. Unless otherwise noted, all parts and percentages are by weight and all temperatures are in degrees Celsius.

Test Methods

As molecular weight indicator of component (A) SRIP I ₂ (ASTM D-1238, Condition 190 ° C./2.16 kg (previously known as “Condition (e)”)) is used.

Proton nuclear magnetic resonance ( ¹ H NMR) is used to determine SRIP styrene content and atactic polystyrene (aPS) concentration. Proton NMR samples are prepared in 1,1,2,2-tetrachloroethane-d ₂ (tce-d ₂ ) to obtain solutions containing 1.6 to 3.2% by weight of polymer, based on the total solution weight. Polymer I ₂ is used as an approximate guideline for determining sample concentration, with 3.2 wt% for I ₂ exceeding ₂ g / 10 min, 2.4 wt% for I ₂ between 1.5 and 2 g / 10 min, 1.6% by weight for I ₂ of less than 1.5 g / 10 min. Suitable apparatus and associated operating conditions are Varian vxr 300 with sample probe at 80 ° C., residual protons of tce-d ₂ at 5.99 ppm, sweep width = 5000 Hz, acquisition time = 3.002 sec, pulse width = 8 μsec, Based on frequency = 300 MHz and delay = 1 sec. As a reference, a sample of polystyrene having a Mw of 192,000 is used.

Process for preparing ethylene-styrene interpolymer (ESI) # 1-3, 5-7

Ingersoll-Dresser biaxial for mixing, using 1H-cyclopenta [1] phenanthren-2-yl) dimethyl (t-butylamido) -silanetitanium 1,4-diphenylbutadiene as catalyst ESI # 1-3, 5-6 are prepared in a continuously operated loop reactor (capacity of 139 liters of 36.8 gallons) equipped with a pump. The residence time is about 25 minutes and liquid is charged to the reactor at 475 psig (3,275 kPa). Feed and feed catalyst / catalyst to pump inlet through injector and KenicsTm static mixer. From the pump to a 2 "diameter line, supplying two in-line Cheminine-Kenics ^TM 10-68 type BEM multi-tube heat exchangers, both containing twisted tape to enhance heat transfer. Release the material As it is discharged in the final exchanger, the loop is recycled through the injector and the static mixer to the inlet of the pump Remove the discharge stream from the loop reactor between the two exchangers.

The solvent is fed to the reactor from two different sources. Fresh toluene stream is used to feed fresh flow to the reactor seal (20 lb / hr (9.1 kg / hr)). Recirculate recycle solvent on the inlet of five 8480-5-E Pulsafeeder ^TM diaphragm pumps connected in parallel to supply solvent and styrene to the reactor at 650 lb / in ² gauge (psi) (4,583 kPa) Mix with styrene monomer.

The ethylene stream is fed to the reactor at 687 psig (4,838 kPa). Hydrogen is introduced into the ethylene stream, then the ethylene / hydrogen mixture is mixed with the solvent / styrene stream in the vicinity and then introduced into the reactor. The mixed stream is cooled to 2 ° C. while entering the reactor loop.

The polymerization is stopped by the addition of a catalyst deactivator (water mixed with solvent) to the product from the reactor, followed by recovery of the product in the form of anhydrous polymer pellets (less than 1000 total volatiles).

Polymerization Method of ESI # 4

ESI # 4 is prepared in a 6 gallon (22.7 liter), oil jack-packed, automatic continuous stirred autoreactor (CSTR) filled with flowing liquid at 475 psig (3,275 kPa): Toluene solvent is added to the reactor at 30 psig (207 kPa) Supply. At 30 psig (207 kPa), unreacted styrene monomer is fed to the reactor. A combined stream is prepared in preparing ESI # 1-3, 5 and 6 using an ethylene feed pressure of 600 psig (4,137 kPa) and fed to the reactor at a temperature of 5 ° C. The polymer product is recovered in the form of anhydrous polymer product in a manner similar to that used to recover ESI # 1-3, and 5-7.

The various catalysts, cocatalysts and processing conditions used to prepare the various respective ethylene styrene interpolymers (ESI # 1-7) are summarized in Table 1 and their properties are summarized in Table 2. All samples were modified with methylaluminoxane (MMAO) (CAS # 146905-) using Tris (pentafluorophenyl) borane (FAB) (CAS # 001109-15-5) (Boulder Scientific) as cocatalyst and as scavenger 79-5) (Akzo Nobel, MMAO-3A). Except for ESI-1, which is prepared using (tert-butylamido) dimethyl (tetramethylcyclopentadienyl) silane-titanium (II) 1,3-pentadiene as catalyst, all ESI is (1H-cyclo Penta [1] -phenanthren-2-yl) dimethyl (tert-butylamido) -silanetitanium 1,4-diphenylbutadiene) is used.

ESI # 8 and ESI # 9 are ESI # 2 and ESI # 3 in Table 15 of WO 98/10015, respectively.

Additional mixtures / foam components

LDPE-1 = LDPE (of 2.4g / 10 minutes I _2, and 0.924g / cm ³ ρ).

LDPE-2 = LDPE (of 1.8g / 10 minutes I _2, and 0.923g / cm ³ ρ).

LDPE-3 = LDPE (of 2.0g / 10 minutes I _2, and 0.924g / cm ³ ρ).

PP-1 = hot melt strength PP (Montell PROFAX ^™ PF814).

PP-2 = homopolymer PP (Montell PROFAX ^™ 6823).

Antioxidant = Iganox ^™ 1010 (Ciba).

Nucleating agent = talc or Hydroserol ^™ CF40E (Möllinger Ingelheim).

Permeable modifier = glycerol monostearate.

Example 1 Ex and Comparative Examples Comp Ex A and B

Foaming products are prepared from the compositions shown in Table 3 at the foaming temperatures shown in Table 3 using a foam apparatus including a single screw extruder, mixer, cooler and foaming die. All samples use Hydrocerol ^™ CF40E (Cöllinger Ingelheim) as the nucleating agent and use Iganox 1010 0.06 phr, glycerol monostearate 0.5 phr, except for Sample 1e, which uses none, all amounts 100 weight of total polymer It is based on wealth. The resulting foams are tested for physical properties as shown in Table 3. The dimensions of the board are 9 to 25 mm thick, 115 to 158 mm wide, with a cross-sectional area exceeding 1000 mm ² .

ρ, continuous bubble content, bubble size, compressive strength (strength at 25% compression), and compression set, respectively, were determined by ASTM Test Methods D3575-93 (Appendix W, Method B), D2856-94, D3573-93 (Appendix B). And according to DIN 53572. Kinetic cushioning C-factor is measured according to ASTM D1596. Compression recovery is measured by compressing the foam to 90% of its original thickness, unloading and then measuring recovery after 24 hours.

As shown in the data in Table 3, the foaming temperature window using the PE / ESI mixture is as wide as 4 ° C (for certain compositions), and for LDPE the foaming window is typically much larger than 1 ° C or less. Surprisingly, LDPE / ESI mixtures foam at temperatures as high as 101-110 ° C., where the temperature range is much higher than the Tg and crystalline melting point of the ESI resin.

Examples 1a-1r show that the inventive mixtures readily provide stable foams having a continuous bubble content in the range of 10-61 vol%. This is in contrast to extruded LDPE where the upper limit of continuous bubbles is typically 20% by volume for stable foams. This is because the viscosity drops rapidly once the temperature exceeds the LDPE crystalline melting point. The viscosity drop subsequently causes a foam drop after the die.

Examples 1b to 1e show that when ESI-3 is used in a mixture with LDPE, isobutane permeates slowly from the foam even when glycerol monostearate is absent and the continuous bubble content is as high as 26% by volume. (In contrast to Comparative Examples A and B). This shows that the mixture of the present invention provides a dimensionally stable foam even in the absence of permeable modifiers.

The data in Table 3 shows that the foams of the present invention have smaller bubbles than the control foams made of LDPE (Comparative Examples A and B). Foams 1e-1i, 1k-1o and 1q-1r have much lower hardness than the LDPE foams of Comparative Examples A and B. Improved ductility and bubble structure are functionally desirable in that they provide a smoother surface with better aesthetics and require a soft touch and less abrasive treatment (eg in the handling of materials in automotive parts). It should be noted that ESI-2 and ESI-3 have a copolymer styrene content of at least 15 mole percent, while ESI-1 has a copolymer styrene content of 10.8 mole percent.

In addition, some LDPE / ESI mixtures (particularly those made of ESI-1 and ESI-3) improve cushioning properties (lower C-factors) compared to foams made only of LDPE. Using the equation C = (G value x foam thickness) / (drop height), where G value is measured according to ASTM D1596 by dropping the load on the foam after aging the foam for 28 days at room temperature. The optimal C-factor is calculated at the static load corresponding to the lowest G value.

Example 2 and Comparative Examples C and D

Example 1 is repeated using a larger extrusion foam line using the composition and process conditions as shown in Table 4. Creep is measured using ASTM D357-93 (Appendix BB).

The data in Table 4 shows that foams made from mixtures of LDPE and ESI-7 (Examples 2a and 2b) have a smoother surface and lower density and compression when using a constant amount of blowing agent compared to comparative foams C and D. Hardening is reduced and compression creep is reduced.

Example 3 Polypropylene / ESI Mixture

A resin mixture of PP and ESI was prepared using a Haake mixing vessel for 8 minutes at a temperature of 190-200 ° C. at 50 rpm. Melt strength tests of pure PP, ESI and LDPE resins as well as mixtures are carried out at 190 ° C. The test involves stretching the strand of molten polymer when it is constantly accelerated until stretching resonance or fracture occurs. The test uses a rhetens device and a capillary rheometer as the take-off device. Record the force required to shorten the strand as a function of the take-up speed. The maximum force before stretching resonance or fracture occurs corresponds to the melt strength. Test conditions include a mass flow rate of 1.35 g / min, a temperature of 190 ° C., a capillary length of 2.1 mm, a piston diameter of 9.54 mm, a piston speed of 0.423 mm / sec, a stretch drop length (die discharge to the take-off wheel) and an acceleration of 100 mm Is 2.4mm / sec ² and cooling is performed using ambient air.

Table 5 summarizes the test results. The data show that the PP / ESI mixture has improved melt elongation (measured in speed) compared to pure PP and is similar to the melt elongation of pure LDPE and ESI (two polymers that are easier to foam than PP). This translates to improving the ability to produce polymeric foams from PP.

Example 4

Using an extrusion foaming apparatus and a strand foam die similar to that used in Example 1, foam planks of coalesced foam strand structure were prepared from the compositions shown in Table 6 at the foaming temperatures shown in Table 6. The composition also includes talc, calcium stearate and Iganox ^™ 1010, each carried out under a load of 0.6 phr per 100 parts by weight of the polymer mixture and use 5.9 phr of isobutane as blowing agent. The die has a number of holes 0.42 inches (1.07 mm) in diameter separated by a distance of 0.144 inches (0.36 cm).

Table 6 summarizes the properties of many foams (measured after aging for 7 days at room temperature (usually 23 ° C.)). Data on bubble size and compressive strength are averaged from three directions (length, width and thickness). The compression set (at 50% compression) is measured according to ASTM test D3575-93.

The data in Table 6 show that the mixture of PP-1 and ESI-5 and ESI-6 provides a stable low density foam having a continuous bubble content in the range of 22 to 88 vol%. The foaming temperature window is as wide as 7 ° C. Increasing the ESI-5 and ESI-6 content from 25% to 50% by weight lowers the compressive strength (known as compression deflection) and lowers the compression set. Lower values of compressive strength indicate that softer foams are obtained.

Example 5 and Comparative Examples E and F

Example 2 was repeated using isobutane as a blowing agent at a concentration of 7.5 phr to prepare a mixture of LDPE-2 and ESI-8 or ESI-9, as shown in Table 7.

The data in Table 7 show that foam disintegration occurs when the content of ESI is high (at least 60% by weight based on the combined weight of components (A) and (B)).

Similar results can be obtained from other mixture compositions, blowing agents and additive combinations, all of which are described herein.

Claims (24)

A polymer foam having a crosslinked gel content of 10% or less and a density of 250 kg / m ³ or less, wherein at least 70% by weight of the polymer in the foam, (A) (1) at least one vinyl or vinylidene aromatic monomer (a), at least one steric hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer (b) or at least one aromatic vinyl or vinylidene monomer and at least one steric hindered 8 to 65 mole% of monomer units derived from mixture (c) of aliphatic or cycloaliphatic vinyl or vinylidene monomers, and (2) 35 to 92 mole percent of monomer units derived from ethylene, aliphatic α-olefins having 3 to 20 carbon atoms or mixtures thereof, One or more substantially random interpolymers 5 to 60 having at least 80 mol% of monomer units derived from components (1) and (2), a melt flow rate of 0.05 to 1000 g / 10 minutes and a crystalline melting point or glass transition temperature of about 80 ° C. or less; Weight percent and (B) contains no monomer units derived from component (1) (a), component (1) (b) or component (1) (c), and contains ethylene, aliphatic α-olefins having 3 to 20 carbon atoms and polarity; A mixture of 95-40% by weight of one or more polymers having at least 80 mol% of monomer units derived from monomers selected from aliphatic α-olefins having 3 to 20 carbon atoms containing groups [content of component (A) and component (B) The mixture, ie based on the total weight of components (A) and (B). 2. The component (A) according to claim 1, wherein component (A) is polymerized from 15 to 65 mol% of component (1) and 85 to 35 mol% of component (2), wherein It is the value calculated by making total molar of 100 mol%), and a foam. The foam according to claim 1 or 2, wherein the continuous bubble content of the foam is 20% by volume or more. The foam according to claim 1 or 2, wherein component (A) (1) is styrene and component (A) (2) is ethylene. The foam according to claim 1 or 2, wherein component (B) is at least one ethylene homopolymer or copolymer having a density of less than 0.94 g / cm ³ and a melt flow rate of 0.01 to 100 g / 10 minutes. The foam according to claim 1 or 2, wherein component (B) is at least one polypropylene homopolymer or copolymer having a melt flow rate of 0.01 to 100 g / 10 minutes. The component (B) according to claim 1 or 2, further comprising 1 to 20 mol% of monomer units derived from at least one ethylenically unsaturated polymerizable monomer, in addition to aliphatic α-olefins having 3 to 20 carbon atoms. Foam. 3 to 20 mole percent of the polymer unit according to claim 1 or 2, wherein component (A) is derived from at least one ethylenically unsaturated polymerizable monomer in addition to component (A) (1) or (A) (2). Foam further containing. The foam according to claim 1, wherein the foam has a density of at least 5 kg / m ³ . The foam according to claim 4, wherein component (A) contains at least 27 mol% of monomer units derived from styrene. The method of claim 1, wherein at least one selected from calcium carbonate, talc, calcium stearate, zinc stearate, clay, silica, barium stearate, calcium stearate, zinc stearate, diatomaceous earth, citric acid, sodium bicarbonate and mixtures thereof Foam further comprising a nucleating agent. The method of claim 1, wherein at least one additive selected from inorganic fillers, pigments, antioxidants, acid scavengers, ultraviolet absorbers, flame retardants, processing aids, extrusion aids, permeability modifiers, antistatic agents, other thermoplastic polymers, and mixtures thereof. Further comprising foam. The method of claim 1, wherein a plurality of channels are formed inside the foam, which channels increase or promote gas permeation exchange regardless of the longitudinal expansion direction of the foam, whereby the blowing agent is released from the foam and air enters the foam. Foam. The polyethylene homopolymer, polypropylene homopolymer, ethylene-vinyl acetate copolymer or ethylene- according to claim 1 or 2, wherein component (B) has a density of less than 0.94 g / cc and a melt flow rate of 0.01 to 100 g / 10 minutes. Foams that are one or more of acrylic acid copolymers. The foam according to claim 1 or 2, wherein the foam has the form of a board having a thickness of 20 mm or more and a width of 50 mm or more, a sheet having a thickness of 1 mm or more and a width of 1000 mm or more, or a rod having a diameter of 40 mm or more. 3. The foam according to claim 1, wherein the foam is shaped as thermoplastic foam beads or expanded and fused thermoplastic foam beads, wherein the beads have an Asker C hardness of less than 80. 4. The foam according to claim 1 or 2, having a unitary foam structure in the form of coalesced strands. The foam according to claim 1 or 2, wherein component (B) is polypropylene modified with at least one coupling agent. 19. The foam according to claim 18, wherein the coupling agent is an azide compound. Converting the mixture into a polymer melt (I), Introducing at least one blowing agent in the polymer melt at elevated pressure in a total amount of 0.2 to 5.0 g-mol per kg of polymer contained in the polymer melt to form a moldable gel (II), Cooling the moldable gel to an optimum temperature (III) and 20. A method of making a polymer foam according to any one of claims 1 to 19, comprising extruding the moldable gel from step (III) through a die into a low pressure region to form a foam. 21. The unitary foam structure of claim 20, wherein the die has a plurality of orifices, wherein the orifice spacing is a strand foam in which the surfaces of adjacent streams of the extrudate are in contact with each other during the foaming step in a low pressure region and the contact surfaces adhere to each other to coalesce. A distance sufficient to bond to a degree sufficient to provide. 21. The method of claim 20, wherein steps (III) and (IV) first accumulate the foamable gel in a foaming delay zone where the temperature and pressure is maintained without foaming the gel and then periodically extruded the gel through the die. To constitute an intermediate process using integrated extrusion means. 21. The method of claim 20, wherein the optimum temperature is a temperature at which no foaming occurs, and step (IV) is modified so that no foaming occurs at all and the resulting extrudate is pelletized to form expandable thermoplastic beads. Converting the mixture into a polymer melt (I), Cooling and granulating the polymer melt to form separated resin particles (II), Producing a suspension by dispersing the resin particles in a substantially insoluble liquid medium (III), Introducing (IV) at least one blowing agent in the suspension at elevated temperature and pressure to be present in a total amount of from 0.2 to 5.0 g-mol / kg based on the total weight of the polymer to form the resin particles into which the blowing agent is incorporated; And 20. The product according to any one of claims 1 to 19, in the form of thermoplastic foam beads, comprising the step (V) of rapidly releasing the product formed from step (IV) into an environment that facilitates conversion to foam beads. Method for producing a foam.