NL1005985C2 - Synthetic foam used for e.g. packaging or automotive applications - Google Patents

Abstract

A foam is prepared using a polymer containing vinyl aromatic compound and unsaturated dicarboxylic acid anhydride and/or imide monomers, and water as a blowing agent. A method for preparing a polymer foam from a polymer mixture and water as a blowing agent, is carried out at high pressure, forming a foam with a fine, uniform cellular structure. The polymer mixture (P) comprises the following components : (A) 50-100 parts first polymer comprising 45-82 mol.% vinyl aromatic compound (A1), 18-35 mol.% anhydride (A2) and/or imide (A3) of an ~a,~b-unsaturated dicarboxylic acid imide, and 0-20 wt.% third monomer (A4); and (B) 0-50 parts by weight second polymer chosen from styrene-acrylonitrile (SAN) polymers and/or a polymer comprising at least 90 mol.% methyl methacrylate (PMMA), to which the following additives can be added (with respect to 100 parts (A) and (B)) : (C) 0-5 parts by weight nucleating agent; (D) 0-8 parts by weight processing aids, fibres, dyes, pigments, fillers and/or stabilisers; (E) 0-10 parts by weight rubber ; (F) at least 0.4 part by weight water and additives in which water is present. An Independent claim is also included for the polymer foam prepared by this method.

Description

- 1 -

POLYMER FOAM FROM WATER FOAMED 5 POLYMER COMPOSITIONS

The invention relates to a process for the production of a polymer foam from a polymer composition, which polymer composition contains a first polymer, which polymer units of a vinyl-aromatic monomer and units of a monomer of an anhydride and / or imide of an α- Contains β-unsaturated dicarboxylic acid monomer, and water as a blowing agent, by reducing the pressure over the high pressure polymer composition such that the polymer composition foams and creates a polymer foam.

Such a method is known from US patent US 4304874. It describes a fire-retardant polymer foam and a method for the production of fire-retardant polymer foams. In the process of US 4304874, a polymer composition consisting of (a) 100 parts of a copolymer consisting of 50 to 25 mole% monovinyl aromatic monomer units and 5 to 50 mole% α-β-unsaturated dicarboxylic anhydride monomer. units; (b) 10 to 20 parts of an at least triple brominated diphenyl ether; and (c) 4 to 8 parts of metal oxide, foamed using 0.5 to 10% by weight of water, by reducing the pressure over the high pressure polymer composition such that the polymer composition foams and creates a polymer foam.

The brominated diphenyl ethers and metal oxides 35 are toxic substances, the presence of which has an adverse effect on the usefulness of the foam in, for example, food applications and on the recycling of the polymer foam.

1005985 - 2 -

However, omission of the brominated diphenyl ethers and / or the metal oxides in the manufacture of a polymer foam according to US 4303874 results in a coarse-cell polymer foam.

The object of the invention is to provide a process for the production of a polymer foam, by a polymer composition, which polymer composition contains a first polymer, which polymer units of a vinyl-aromatic monomer and 10 units of a monomer of an anhydride and / or imide of a α-β-unsaturated dicarboxylic acid monomer, and water as a blowing agent, by reducing the pressure over the polymer composition under high pressure such that the polymer composition 15 foams, producing a polymer foam that does not overcome the disadvantages related to recycling and food applications or has a greatly reduced degree and which has a low density and fine, uniform cells.

Surprisingly, this object is achieved by using a polymer composition consisting of a) 50-100 parts of the first polymer, the first polymer consisting of 45 to 82 mol% of units 25 of a vinyl aromatic monomer and 18 to 35 mol % of units of a monomer of an anhydride and / or imide of an α-β-unsaturated dicarboxylic acid and 0-20 mol% of units of a third monomer b) 50-0 parts by weight of the second polymer, being a polymer containing monomer units styrene and

acrylonitrile (SAN) or a polymer containing at least 90 mol% monomer units of methyl methacrylate (PMMA) or a mixture of SAN and PMMA

100 parts of the first and second polymer together being present c) 0-5 parts by weight of nucleating agent d) 0-8 parts by weight of one or more components from the group of processing aids, fibers, dyes, 1005985-3 pigments, fillers, stabilizers, anti-oxidants, lubricants and plasticizers e) 0-10 parts by weight of rubber f) at least 0.4 parts by weight of water and optionally 5 residues of additives from which the water has been released, per 100 parts of polymer composition. This creates a polymer foam with fine, uniform cells.

A further advantage is that with the method according to the invention polymer foams are obtained which are closed-cell foams. Still further advantages of polymer foams obtained with the method according to the invention are the high specific compressive strength, the high specific stiffness and the high specific strength. Specific in this context means that it is standardized on the density of the polymer foam. A still further advantage is the absence of residual harmful propellants in the polymer foams.

A further advantage is that such polymer foams can also be foamed with the same result after a relatively long time, so independent of the age of the foam. For the known foams there is usually a period in which the post-foaming proceeds optimally, for instance the period between 1 and 2 months after production of the foam.

A still further advantage is the temperature resistance of polymer foams prepared by the method according to the invention. A still further advantage of the polymer foam is that they are made with little nucleating agent. The presence of germinating agents or remnants of germinating agents increase the density.

Examples of vinyl aromatic monomers which can be used in the first polymer are styrene, α-methylstyrene, paramethylstyrene or mixtures thereof. Preferably styrene monomer units 4 Λ η η λ tz - 4 - are used.

Examples of α-β unsaturated dicarboxylic anhydride monomers which can be used in the first polymer, which is part of the polymer composition used according to the process of the invention, are maleic anhydride, citraconic anhydride, cyclohexylmaleic anhydride, benzylmaleic anhydride, itoconic anhydride, phenylmaleic anhydride, aconitic anhydride, propylmaleic anhydride, 1,2-diethylmaleic anhydride and mixtures thereof. Preferably maleic anhydride monomer units are used. Even more preferably, a polymer of 15 styrene and maleic anhydride monomer units is used.

Examples of imides of α-β unsaturated dicarboxylic acid monomers which can be used in the first polymer, which is part of the polymer composition used according to the method of the invention, are the imides of the anhydrides mentioned above and mixtures thereof. Preferably monomer units of the imide of maleic anhydride are used. Even more preferably, a polymer of styrene monomer units and monomer units of an imide of maleic anhydride is used.

The first polymer, which contains vinyl aromatic monomer units and monomer units of an anhydride of an α-β-unsaturated dicarboxylic acid monomer, can be prepared by any of the known methods, as described, for example, in Hanson and Zimmerman, Ind. Scary. Chem. Full. 49, No. 11 (1957) p. 1803-1807. The imidization can take place, for example, as described in EP 0 728 767 A1. To imidize the anhydrides, ammonia, aromatic amines, for example alpha-naphthylamine, aniline or 1005985-5-substituted aniline, and urea derivatives, for example urea and diphenylurea, are used. Alkylamines, caprolactam, amine-modified poly-dimethylsiloxanes and polyetheramines, for example, amine-modified polyethylene oxide, amine-modified polypropylene oxide and block copolymers thereof, can be used. Aniline is preferably used.

In addition to vinyl aromatic monomer units and 10 monomer units of anhydrides and / or imides of α-β-unsaturated dicarboxylic acids, the first polymer may also contain third monomer momomer units of, for example, acrylic acid, methacrylate, an ester of these acids, acrylonitiril, etc. Also, for example, if styrene is used as a vinyl aromatic monomer, alpha methyl styrene can be used as a third monomer.

The choice of the third monomer and / or the choice of the substance with which it is optionally imidized influences the polarity of the polymer foam. In this way, a polymer foam with a relatively polar or relatively non-polar surface can be obtained.

Preferably SAN and / or PMMA as the second polymer form part of the polymer composition used in the method according to the invention. Examples of PMMA are, in addition to pure polymethyl methacrylate, polymers which, in addition to methyl methacrylate monomer units, also contain, for example, monomer units ethyl acrylate and / or methyl acrylate. An advantage of SAN and / or PMMA-containing compositions is that the use of such polymer compositions results in polymer foams with a higher toughness. The production process of this type of foams is also less sensitive to fluctuations in the conduct of the process.

Examples of nucleating agents which can be used in the method according to the invention 1005985-6 are talc and chalk. Talc is preferably used. The amount of nucleating agent in the polymer composition according to the invention is preferably 0.1-3 parts nucleating agent per 100 parts of polymer. Even more preferably, 0.1-1 parts nucleating agent per 100 parts polymer is used.

All kinds of processing aids, fibers, dyes, pigments and fillers can be added to the polymer composition used in the method according to the invention, provided that these components do not prevent the action of the water as a blowing agent.

Rubber can also be added to the polymer composition used in the method according to the invention. Rubber is optionally used to increase the processability of the polymer foam to finished products and the tear resistance of the polymer foam. The rubber-containing polymer foams are also tougher.

Examples of rubbers are polybutadiene rubber, ethylene-propylene rubber (EPM rubber), ethylene-propylene diene monomer rubber (EPDM rubber), acrylonitrile butadiene styrene (ABS) and polybutyl acrylate rubber. The person skilled in the art is familiar with suitable combinations of rubbers and the first and second polymer, which form part of the polymer composition according to the method.

It is possible to add the water in the known ways, for example by injecting water into the melt of the polymer composition in a foam-making processing unit equipped with an injection unit, by mixing the polymer composition with salts containing crystal water, by impregnating granules of the polymers containing the polymer composition with water and then using them in the polymer composition, and by conducting a chemical reaction, for example 1005985-7 - an imidation reaction, releasing water as a reaction product. When diphenylurea is used to imidize the maleic anhydride, CO2 is formed in addition to H 2 O and the imidation product. In addition to water, the gaseous CO2 will also act as a blowing agent and contribute to the formation of slime. In the presence of CO2, less nucleating agent needs to be added. When water is added by carrying out an imidization reaction, diphenyl urea is preferably used as the reactant. Preferably, the water used as a blowing agent is injected into the polymer composition.

The amount of water used depends on the desired density of the foam.

There should be enough water for the polymer composition to foam to the desired density. However, too much water leads to premature foaming, that is to say that the polymer composition 20 already foams in the foaming processing apparatus instead of just outside the head, resulting in an irregularly structured foam. In the method according to the invention, preferably 0.4-25 parts by weight of water per 100 parts of polymer are used.

Even more preferably, 2-6 parts by weight of water per 100 parts of polymer is used. Equipment suitable for foaming polymer compositions is known to the person skilled in the art. The polymer composition prepared according to the invention can, for example, be placed in an extruder or injection molding machine suitable for the production of polymer foams, preferably provided with an injection unit suitable for a controlled dosing of the water, and mixed therein and heated under pressure. Static mixers / coolers are preferably still present on the exit side of the extruder. Preferably, a tandem extruder is used in the 1C05985-8 method of the invention. The tandem extruder is a combination of two successive concatenated extruders, the first of which has a dispersing function and the second a cooling function.

The temperature selected for foaming the polymer composition after heating depends on the polymer composition and can be determined by those skilled in the art. In general, the temperature of the static mixers / coolers or of the second extruder in a tandem extruder is 20 to 30 ° C higher than the glass transition temperature of the polymer composition. For example, the pressure in the extruder head is between 50 and 250 bar. Preferably a minimum pressure of 50 bar is used.

The invention also relates to polymer foams obtainable by the method according to the invention. Preferably, these polymer foams are low density foams with fine uniform cells. Although it is known from US patent US 5 439 946 foams of a polymer containing monomer units of a vinyl-aromatic monomer and units of a monomer of an anhydride and / or imide of an α-β-unsaturated dicarboxylic acid monomer, but the polymer foams available with the method according to the invention are more processable into end products and have a higher tear resistance than the polymer foams from US 5 439 946. Another advantage is that the polymer foams available with the method according to the invention can have lower densities than the foams from US 5 439 946. Another advantage of polymer foams obtainable with the method according to the invention is the lack of a limitation in the minimum achievable density in relation to the mole percentage of maleic acid or maleic anhydride.

The densities of the polymer foams available from 1005985-9 with the method according to the invention are preferably between 25 kg / m3 and 250 kg / m3. In this text, unless stated otherwise, density is meant after foaming, and thus before possibly after foaming. Even more preferably, the polymer foams have a density between 25 and 100 kg / m3.

The polymer foams can for instance be manufactured in the form of plates, profiles, tubes, flakes and the like. These can be used, for example, in the packaging industry and the automotive industry.

The invention is elucidated on the basis of exemplary experiments without being limited thereto.

Comparative experiment A

A polymer composition consisting of (a) a first polymer with 86 mole% styrene and 14 mole% maleic anhydride monomer units; (molecular weight 190,000 g / mol), and (b) 2 parts by weight of talc masterbatch, consisting of 40% by weight talc and 60% by weight styrene-acrylonitrile (SAN), was heated in a single screw extruder with a screw diameter of 25mm, and a screw length of 900mm, supplied by

Schwabenthan Germany. The speed was 40 rpm. The extruder was equipped with an injection unit for the water injection. The water injection was just in front of the extruder's dispersing unit. The pump of the 30 injection unit was a plunger pump, type Gilson 305. The end of the extruder, after the dispersing unit, was equipped with static mixers / coolers (Sulzer brand), with an inner diameter of 30 mm and an L / D- ratio of 30. The nozzle of the head was rectangular (5mm 35 by 1mm). The throughput of the polymer composition was 3 kg / hour. 2 cc / min (4 weight percent) of water was injected. The temperature of the static 1005985-10 mixers / coolers was 160 ° C. The polymer foam obtained had a density of 50 kg m-3. The density was measured by first determining the weight of a piece of foam by weighing, and then determining the volume of the same piece of foam by immersion in water in a measuring glass. The density is the quotient of the weight and volume, in kg / m3. The foam had an open cellness of 17%, measured according to ASTM D2856-87. The open cell meter was from the Beekman brand, model 10 930 Air Comparison Pycnometer, and cell diameters from 2500 to 3500 μτα. Cell diameters were determined from Scanning Electron Microscope (SEM) photos (10X magnification).

Comparative experiment B

A polymer composition comprising (a) a first polymer with 88 mole% styrene and 12 mole% maleic anhydride monomer units; (110,000 g / mol mol), and (b) 2 parts by weight of talc masterbatch, consisting of 40 percent by weight talc and 60 percent by weight styrene-acrylonitrile (SAN), was prepared as described in comparative experiment A, and then extruded. The polymer foam obtained was characterized using the methods described in comparative experiment A. The polymer foam obtained had a density of 42 kg m-3. The foam had an open cellity of 24% and cell diameters from 800 to 3000 µm.

30 Example 1

A polymer composition consisting of (a) a first polymer consisting of 82 mole% styrene and 18 mole% maleic anhydride monomer units (110,000 g / mole molecular weight) and (b) 2 parts by weight of 35 talc masterbatch consisting of 40 wt% talc and 60 wt% SAN, was prepared as described in comparative experiment A, and then extruded 1005985-11. The static mixer temperature was 165 ° C and the pressure was 105 bar. The head temperature was 175 ° C and the head pressure 85 bar.

For the characterization of the polymer foam, the same methods and standards were used as in comparative experiment A. The polymer foam obtained had a density of 49 kg πΓ3, an open cellity of 6% and cell diameters of 400 to 1700 f / m.

10

Example 2

A polymeric composition consisting of (a) a first polymer, consisting of 72 mole% styrene and 28 mole% maleic anhydride monomer units 15 (molecular weight 110,000 g / mole); and (b) 2 parts by weight of talc masterbatch, consisting of 40 percent by weight talc and 60 percent by weight SAN, was prepared as in comparative experiment A, and then extruded. The static mixer temperature was 190 ° C and the pressure 20 was 100 bar. The head temperature was 205 ° C and the pressure 70 bar.

The same methods and standards were used for the characterization of the polymer foam as in comparative experiment A.

The resulting polymer foam had a density of 42 kg m ~ 3, an open cellity of 9% and cell diameters from 200 to 1100 µm.

Example 3 A polymer composition consisting of (a) a first polymer consisting of 72 mol% styrene and 10 mol% maleic anhydride and 18 mol% maleic imide monomer units (molecular weight 130,000 g / mol), (b) 2 parts by weight of talc masterbatch, consisting of 40 weight percent talc and 60 weight percent SAN, was prepared as in comparative experiment A, and then extruded. The temperature of the cup was 1005985 - 12 - 200 ° C and the pressure 73 bar.

The same methods and standards were used for the characterization of the polymer foam as in comparative experiment A.

The polymer foam obtained had a density of 50 kg m-3, an open cellity of 5% and cell diameters of 200 to 1100 µm.

Example 4 A polymer composition consisting of (a) 50 parts of a first polymer, consisting of (a) 75 mol% of styrene and 25 mol% of maleic anhydride monomer units (molecular weight 200,000 g / mol), and (b) 50 parts of a second polymer, in this case styrene-15 acrylonitrile (SAN, type Luran2795, Mw 200,000 g / mol, acrylonitrile content 26 mol%) and (c) 2 parts by weight of talc masterbatch, consisting of 40% by weight talc and 60% by weight SAN , was dry blended in a tumbler prior to use. This mixture was heated in a 30mm diameter single screw extruder supplied by Schwabenthan Germany. The speed of the extruder was 40 rotations per minute (RPM). The extruder was equipped with an injection unit and with static mixers / coolers (L / D 25 = 30). The throughput of the polymer composition was 3 kg / hour. 3 cc / min (6 weight percent) of water was added. The temperature of the static mixers / coolers was 150 ° C. The temperature of the cup was 160 ° C and the pressure 150 bar. The same methods and standards were used for the characterization of the polymer foam as in comparative experiment A.

The polymer foam obtained had a density of 44 kg in-3, an open cell density of 4%, and cell diameters of 300 to 1200 µl.

35

Example 5

A polymer composition consisting of (a) 1 005985-13 - a first polymer consisting of (a) 75 mol% of styrene and 25 mol% of maleic anhydride monomer units (molecular weight 200,000 g / mol), and (b) 10 parts diphenylurea (SIGMA, 98% pure) and (c) 0.2 parts of paratoluene sulfonic acid (PTSZ) were mixed in a tumbler. PTSZ catalyzes the imidization reaction and acts as a nucleating agent. The polymer composition was heated in a single screw extruder with a diameter of 30mm and an L / D of 30 supplied by Schwabenthan Germany. The speed of the extruder was 40 RPM. The extruder was equipped with static mixers / coolers. The throughput of the polymer composition was 3 kg / hour. The temperature of the static mixers / coolers was 195 ° C. The temperature of the cup was 200 ° C and the pressure 105 bar. The same methods and standards were used for characterizing the polymer foam as in comparative experiment A.

The polymer foam obtained had a density of 50 kg m 3, an open cellity of 13% and cell diameters of 100 to 500 µm.

The results of the comparative experiments and the examples show that when a polymer composition is used according to the method of the invention, a low density foam is obtained with fine uniform cells, with a higher content of units of an anhydride and / or an imide of an α- (3-unsaturated dicarboxylic acid) leads to polymer foams with finer cells.

1 005985

Claims (17)

1. A process for the manufacture of a polymer foam from a polymer composition, said polymer composition containing a first polymer, said polymer units of a vinyl aromatic monomer and units of a monomer of an anhydride and / or imide of an α-β-unsaturated 10 contains dicarboxylic acid monomer, and water as a blowing agent, by reducing the pressure over the polymer composition under high pressure, such that the polymer composition foams and a polymer foam is obtained, characterized in that a polymer composition is used, consisting of * a) 50-100 parts of the first polymer, the first polymer consisting of 45 to 82 mol% of 20 units of a vinyl aromatic monomer and 18 to 35 mol% of units of a monomer of an anhydride and / or imide of an α -β-unsaturated dicarboxylic acid and 0-20% in units of a third monomer b) 50-0 parts by weight of the second polymer, being a polymer containing styrene and acrylonitrile (SAN) monomer units or a polymer containing at least 90 mole% methyl methacrylate (PMMA) monomer units or a mixture of SAN and 30 PMMA with 100 parts of the first and second polymer together c) 0-5 parts by weight of nucleator d) 0-8 parts by weight from a group of 35 processing aids, fibers, dyes, pigments, fillers and stabilizers, e) 0-10 parts by weight of rubber 1005985 - 15 - f) at least 0.4 parts by weight of water and any residues of additives from which the water has been released, per 100 parts of polymer composition, so that a polymeric foam with fine, uniform cells is obtained. A method according to claim 1, characterized in that water is used as water injected. A method according to any one of claims 1-2, characterized in that the vinyl aromatic monomer is styrene. A method according to any one of claims 1-3, characterized in that the anhydride of an α-β-unsaturated dicarboxylic acid monomer is maleic anhydride. A method according to any one of claims 1-4, characterized in that 0-10 units of the third monomer form part of the first polymer in the polymer composition. A method according to any one of claims 1 to 5, characterized in that the imide of an α-β-unsaturated dicarboxylic anhydride monomer is the imide of maleic anhydride. A method according to any one of claims 1-6, characterized in that the polymer composition contains 0.1-3 parts by weight nucleating agent per 100 parts polymer. A method according to any one of claims 1-7, characterized in that the polymer composition 0.1-1 contains 30 parts by weight nucleating agent per 100 parts polymer. A method according to any one of claims 1-8, characterized in that the polymer composition contains talc as a nucleating agent. A method according to any one of claims 1-9, characterized in that the polymer composition contains 0.1-3% by weight of one or more components from a 1005985-16 group of processing aids, fibers, dyes, pigments, fillers, stabilizers, anti-oxidants , lubricants and plasticizers. A method according to any one of claims 1-10, characterized in that the polymer composition contains 0.4-10 parts by weight of water. A method according to claims 1-11, characterized in that the polymer composition with 2-6 contains 10 parts by weight of water. A method according to any one of claims 1-12, characterized in that the temperature of the part of a processing device suitable for foaming fulfilling the cooling function is 20 to 30 ° C higher than the glass transition temperature of the polymer composition. Polymeric foam consisting of a) 50-100 parts of the first polymer, the first polymer consisting of 45 to 82 mol% of 20 units of a vinyl aromatic monomer and 18 to 35 mol% of units of a monomer of a anhydride and / or imide of an α-β-unsaturated dicarboxylic acid and 0-20% of units of a third monomer b) 50-0 parts by weight of the second polymer, being a polymer containing monomer units styrene and acrylonitrile (SAN) or a polymer containing at least 90 mol% methyl methacrylate monomer units (PMMA) or a mixture of SAN and PMMA, in which 100 parts of the first and the second polymer together are present c) 5 or less than 5 parts by weight of nucleating agent or remnants of nucleating agent 35 d) 0-8 parts by weight of one or more components from the group of processing aids, fibers, dyes , pigments, fillers, 1005985-17 - stabilizers, anti-oxidants, lubricants and plasticizers e) 0-10 parts by weight of rubber f) at most 10 parts by weight of water and optionally 5 residues of additives from which the water has been released per 100 parts of polymer composition. Polymer foam according to claim 14, characterized in that the polymer foam contains at most 1 part by weight of water and any residues of additives from which the water has been released per 100 parts of polymer. Foamed polymer composition according to any one of claims 14-15, characterized in that the polymer foam has a density of 25 to 250 kg / m3, the density being the density after foaming but before any subsequent foaming. Foamed polymer composition according to any one of claims 14-16, characterized in that the polymer foam has a density of 25-100 kg / m3, the density being the density after foaming but before any subsequent foaming. 1005985