WO2019062731A1

WO2019062731A1 - Process for extrusion moulding polymer compounds comprising poly (meth) acrylimide foam particles

Info

Publication number: WO2019062731A1
Application number: PCT/CN2018/107456
Authority: WO
Inventors: Ricardo Luiz Willemann; Qianwen KONG; Denis HOLLEYN; Zhenyuan SHI; Kaifeng YAN
Original assignee: Evonik Specialty Chemicals Shanghai Co Ltd
Current assignee: Evonik Specialty Chemicals Shanghai Co Ltd
Priority date: 2017-09-28
Filing date: 2018-09-26
Publication date: 2019-04-04
Anticipated expiration: 2020-03-28

Abstract

L'invention concerne un procédé de moulage par extrusion d'un composé polymère comprenant une résine thermoplastique qui peut être traitée à l'état fondu à des températures inférieures à 400°C et des particules de mousse de poly(méth)acrylimide (P(M)I) qui conservent la forme particulaire à une température supérieure d'au moins 120℃ à la T g de la résine thermoplastique. Le procédé comprend les étapes consistant à: (a) chauffer le composé polymère à une température supérieure de 120-240℃ à la T g de la résine thermoplastique et (b) mouler par extrusion le composé polymère dans un moule dans des conditions de pression d'extrusion de 5-300 bars pour obtenir un extrudat. L'extrudat obtenu au moyen du procédé de la présente invention atteint un poids léger significatif par comparaison avec la référence, et peut être largement utilisé dans une conception légère.The invention relates to a process for the extrusion molding of a polymeric compound comprising a thermoplastic resin which can be melt processed at temperatures below 400 ° C and poly (meth) acrylimide foam particles (P ( M) I) which retain the particulate form at a temperature at least 120 ℃ higher than the T g of the thermoplastic resin. The method comprises the steps of: (a) heating the polymer compound to a temperature greater than 120-240 ℃ at the T g of the thermoplastic resin and (b) extrusion molding the polymer compound in a mold under pressure conditions 5-300 bar extrusion to obtain an extrudate. The extrudate obtained by the method of the present invention achieves a significant light weight compared to the reference, and can be widely used in a lightweight design.

Description

PROCESS FOR EXTRUSION MOULDING POLYMER COMPOUNDS COMPRISING POLY (METH) ACRYLIMIDE FOAM PARTICLES

Field of the invention

The invention relates to a process for extrusion moulding polymer compounds comprising poly (meth) acrylimide (P(M) I) foam particles, in particular polymethacrylimide (PMI) foam particles.

Background

Poly (meth) acrylimide foams e.g. polymethacrylimide foams, such as those marketed under the trademark

by Evonik Resource Efficiency GMBH, are widely used in composite material for light weight design in the aerospace, automotive, sport and medical device industries, etc. due to their light weight and high mechanical performance.

In the past, the P (M) I foams were supplied in the shape of blocks, which however did not quite fit the processing of parts with complex 3D geometries, and could result in long cycle time, low precision, and material waste.

WO2013/056947 describes a mould shaping process of P (M) I foams which partially solves the above problems, wherein (prefoamed) P (M) I polymer particles are foamed in a mould with the aid of adhesives, which can be a polyamide or a poly (meth) acrylate. The dose of the adhesives can be up to 20%of the P (M) I polymer particles, i.e. up to 16.7%based on the total weight of the P (M) I polymer particles and the adhesive. However this process still results in long cycle time.

PCT/CN2017/078572 describes a polymer compound comprising poly (meth) acrylimide (P (M) I) foam particles. PCT/CN2017/102026 describes a process for injection moulding the polymer compound. The present inventors further explored the process for extrusion moulding the polymer compound and accomplished the present invention.

Summary of the present invention

The present invention provides a process for extrusion moulding a polymer compound comprising:

(1) 20-99%a thermoplastic resin, which is melt processible at temperatures of less than 400℃, and

(2) 1-80%poly (meth) acrylimide (P (M) I) foam particles, which maintain the particulate form at a temperature at least 120℃ higher than the T _g of the thermoplastic resin, based on the total weight of the polymer compound, said process including steps of:

(a) heating the polymer compound to a temperature 120-240℃ higher than the T _g of the thermoplastic resin where the thermoplastic resin melts and the poly (meth) acrylimide (P (M) I) foam particles maintain the particulate form, and

(b) extrusion moulding the polymer compound under an extrusion pressure of 5-300 bar to obtain an extrudate.

T _g refers to glass transition temperature, which can be determined by the DSC method according ISO 1135.

The present inventor has found it is important to control the temperature and pressure during the extrusion moulding process so as to provide sufficient flowability of the polymer compound, and to avoid the damage of the cell structure of the foam particles.

The extrudate obtained from the process of the present invention can achieve light weight. And it is surprisingly found that the same light weight can be achieved with less P (M) I foam load in the polymer compound in the present invention, compared with an injection moulding process.

The present invention also provides the extrudate obtained from the process of the present invention.

The present invention further provides the use of the extrudate of the present invention in light weight design.

Detailed description of the present invention

Preferably, in step a) the temperature is 130-220℃, more preferably 140-200℃ higher than the T _g of the thermoplastic resin.

Preferably, in step b) the extrusion pressure is 10-200 bar, preferably 10-100 bar.

Preferably, the extrudate is in the form selected from profiles, sheets, films, tubes, cylinders, cubes, rods, ribbons and meshes.

There is no limitation to the thermoplastic resin as long as it is melt processible at temperatures of less than 400℃. Melt processible is used in its conventional sense, that the polymer can be processed at the indicated temperatures without substantial degradation of the polymer.

Examples of the thermoplastic resin include polyamides, polyolefins, polyesters and copolymers containing any of the above segments as well as the blend thereof.

Preferably, the polyamide is selected from aliphatic polyamides, more preferably PA6, PA11, PA12, PA46, PA66, PA10, PA610, PA612, PA1010, PA1012 and the blend thereof.

The P (M) I foam particles used in the present invention can be obtained by the granulation of the P (M) I foams which are not in particulate form.

The P (M) I foams are also termed rigid foams, and feature particular robustness. The P (M) I foams are normally produced in a two-stage process: a) production of a cast polymer, and b) foaming of said cast polymer. In accordance with the prior art, these are then cut or sawn to give the desired shape.

Production of the P (M) I foams begins with production of monomer mixtures which comprise (meth) acrylic acid and (meth) acrylonitrile, preferably in a molar ratio of from 2: 3 to 3: 2 as main constituents. Other comonomers can also be used, examples being esters of acrylic or methacrylic acid, styrene, maleic acid and itaconic acid and anhydrides thereof, and vinylpyrrolidone. However, the proportion of the comonomers here should not be more than 30%by weight. Small quantities of crosslinking monomers can also be used, an example being allyl acrylate. However, the quantities should preferably be at most from 0.05%by weight to 2.0%by weight.

The copolymerization mixture moreover comprises blowing agents which at temperatures of about 150 to 250℃ either decompose or vaporize and thus form a gas phase. The polymerization takes place below this temperature, and the cast polymer therefore comprises a latent blowing agent. The polymerization advantageously takes place in a block mould between two glass plates.

The cast polymer is then foamed at an appropriate temperature in a second step. The production of such P (M) I foams is known in principle to a person skilled in the art and can be reviewed in EP 1 444 293, EP 1 678 244 or WO 2011/138060 for example.

The P (M) I foam particles used in the present invention can also be obtained by the foaming of the P (M) I polymer particles.

The P (M) I polymer particles can be obtained by grinding the cast polymer, for example, in a cutting mill. The grindings are then foamed at an appropriate temperature to produce the P (M) I foam particles.

Preferably, the P (M) I foam particles used in the present invention is obtained by the foaming of the P (M) I polymer particles, where the closed foam cells are not destroyed, compared with the P (M) I foam particles obtained by the granulation of the P (M) I foams.

Preferably, the P (M) I foam particles have a grain size which ranges 0.1-30 mm, more preferably 0.5-10 mm.

Preferably, the P (M) I foam particles have a bulk density of 25-220 kg/m ³, more preferably 50-150 kg/m ³.

In one embodiment of the present invention, the P (M) I foam particles are polymethacrylimide (PMI) foam particles.

PMI polymers and/or foams, commercially available from Evonik Resource Efficiency GMBH, may be mentioned in particular.

Preferably, the polymer compound comprises

30-99%, more preferably 40-99%the thermoplastic resin, and,

1-70%, more preferably 1-60%the P (M) I foam particles,

based on the total weight of the polymer compound.

Preferably, the thermoplastic resin is melt processible at temperatures of less than 250℃, and/or the P (M) I foam particles maintain the particulate form at a temperature at least 140℃, preferably at least 180℃ higher than the T _g of the thermoplastic resin.

The polymer compound of the present invention may include additives, such as calcium carbonate, glass beads, zinc oxide, and fiber reinforcements such as ceramic fibers, aramid fibers, potassium titanate fibers, glass fibers and carbon fibers, depending on the effect or performance desired.

The extrudates obtained from the process of the present invention are generally suitable in principle for any type of lightweight design, and can in particular be used in mass production by way of example for structural parts in the automobile industry, in rail vehicle construction or shipbuilding, in the aerospace industry, in mechanical engineering, in the production of sports equipment, in furniture construction or in the design of wind turbines.

Examples

The PMI foam particles used in the examples were prepared from PMI polymer particles marketed with trademark

Triple F by Evonik Resource Efficiency GMBH. The PMI polymer particles were produced from a fully polymerized copolymer sheet (which had not been prefoamed) with the aid of a granulator. The grain size range of the particles used in the examples, after sieving to keep the fines, was below 1.0 mm. The bulk density of the PMI polymer particles was about 600-700 kg/m ³.

The PMI polymer particles were foamed in an oven at a temperature of 200-240℃ for 30-60 mins. The obtained PMI foam particles had a bulk density of 100-150 kg/m ³ and a grain size of 0.5-5 mm.

The PMI foam particles were mixed with the melts of a PA12 (

L1600, Tg = 20-30℃, commercially available from Evonik Resource Efficiency GMBH) to prepare compounds 5 : 95, 7.5 : 92.5 and 10 : 90 (part by weight) , which were shaped into tubes by extrusion moulding in an extruder (Maillefer Extrusion NMC 45-24D) equipped with a tube die having an external diameter of 16 mm and an inner diameter of 12 mm according to process parameters indicated in Table 1 below.

The extrudates in tube form were tested for density (ISO 1183) and the result is also indicated in Table 1 below.

Table 1 Extrusion moulding

*Example 1 was a reference where only the polyamide of

L1600 was shaped.

It can been seen that that extrudates of the examples achieve significant light weight compared with the reference.

An injection moulding specimen with a density close to Example 4 was also prepared for comparison.

The PMI foam particles were mixed with the melts of a PA12 (

L1600, commercially available from Evonik Resource Efficiency GMBH) to prepare a compound, which was shaped into plates having a thickness of 5 mm by injection moulding in an injection machine (Engel Victory 200/110 Tech Pro) according to process parameters indicated in Table 2 below.

The specimen was tested for density (ISO 1183) and the result is also indicated in Table 2 below.

Table 2 Injection moulding

It can be seen that the load of PMI foam particles in the polymer compound reaches 50%for the moulding part obtained by an injection moulding process to achieve a density of 0.73 g/cm ³, while in Example 4 of the present invention, the load of the PMI foam particles is 7.5%to achieve a density of 0.71 g/cm ³. It is believed that the extrusion moulding process of the present invention would need much less load of the PMI foam particles to achieve the same light weight effect compared with an injection moulding process.

Meanwhile, extrusion moulding is a continuous process. It is believed that the extrusion moulding process of the present invention would be more time efficient to achieve the same light weight than an injection moulding process.

Extrudates in tube form with higher load of PMI foam particles were also successfully prepared according to procedures similar to Examples 1-7. These extrudates were also tested for density (ISO 1183) and the result is indicated in Table 3 below.

Table 3 Extrusion moulding (high foam load)

*Example 10 was a reference where only the PA12 composition of

LX9012 (commercially available from Evonik Resource Efficiency GMBH) was shaped.

It can be seen that the extrusion moulding process of the present invention also works with polymer compound with high foam load (e.g. 60%) and the obtained extrudates achieve very significant low weight.

Claims

A process for extrusion moulding a polymer compound comprising:

(1) 20-99%a thermoplastic resin, which is melt processible at temperatures of less than 400 ℃, and

(2) 1-80%poly (meth) acrylimide (P (M) I) foam particles, which maintain the particulate form at a temperature at least 120 ℃ higher than the T _g of the thermoplastic resin,

based on the total weight of the polymer compound,

said process including steps of:

(a) heating the polymer compound to a temperature 120-240 ℃ higher than the T _g of the thermoplastic resin where the thermoplastic resin melts and the poly (meth) acrylimide (P (M) I) foam particles maintain the particulate form, and

(b) extrusion moulding the polymer compound under an extrusion pressure of 5-300 bar to obtain an extrudate.
The process according to claim 1, wherein in step a) the temperature is 130-220 ℃, preferably 140-200 ℃ higher than the T _g of the thermoplastic resin.
The process according to any one of the preceding claims, wherein in step b) the extrusion pressure is 10-200 bar, preferably 10-100 bar.
The process according to any one of the preceding claims, wherein the extrudate is in the form selected from profiles, sheets, films, tubes, cylinders, cubes, rods, ribbons and meshes.
The process according to any one of the preceding claims, wherein the thermoplastic resin is selected from polyamides, polyolefins, polyesters and copolymers containing any of the above segments as well as the blend thereof, preferably from aliphatic polyamides, more preferably from the group consisting of PA6, PA11, PA12, PA46, PA66, PA10, PA610, PA612, PA1010, PA1012 and the blend thereof.
The process according to any one of the preceding claims, wherein the P (M) I foam particles have a grain size which ranges 0.1-30 mm, preferably 0.5-10 mm, and /or a bulk density of 25-220 kg/m ³, preferably 50-150 kg/m ³.
The process according to any one of the preceding claims, wherein the P (M) I foam particles are obtained by the granulation of P (M) I foams which are not in particulate form, or the foaming of P (M) I polymer particles.
The process according to any one of the preceding claims, wherein the P (M) I foam particles are polymethacrylimide (PMI) foam particles.
The process according to any one of the preceding claims, wherein the polymer compound comprises:

30-99%, preferably 40-99%the thermoplastic resin, and

1-70%, preferably 1-60%the P (M) I foam particles,

based on the total weight of the polymer compound.
The process according to any one of the preceding claims, wherein

the thermoplastic resin is melt processible at temperatures of less than 250 ℃,

and /or

the P (M) I foam particles maintain the particulate form at a temperature at least 140 ℃, preferably at least 180 ℃higher than the T _g of the thermoplastic resin.
The process according to any one of the preceding claims, wherein the polymer compound is in situ made in step a) by physically mixing the P (M) I foam particles and the melt of the thermoplastic resin.
The extrudate obtained from the process according to any one of the preceding claims.
Use of the extrudate according to claim 12 in light weight design.