WO2014001119A1

WO2014001119A1 - Method for producing expandable granulates containing polylactic acid

Info

Publication number: WO2014001119A1
Application number: PCT/EP2013/062507
Authority: WO
Inventors: Jerome LOHMANN; Bangaru Dharmapuri Sriramulu Sampath; Peter Gutmann; Andreas KÜNKEL; Klaus Hahn; Andreas Füssl
Original assignee: Basf Se; Basf Schweiz Ag
Priority date: 2012-06-26
Filing date: 2013-06-17
Publication date: 2014-01-03

Abstract

The invention relates to a method for producing expandable granulates containing polylactic acid, comprising the steps: a) melting and mixing the components i) 61.9 to 98.9% w/w, in relation to the total weight of components i to iv, of polylactic acid, ii) 1 to 38% w/w, in relation to the total weight of components i to iv, of at least one polyhydroxyalkanoate, iii) 0 to 30% w/w, in relation to the total weight of components i to iv, of at least one polyester based on aliphatic and/or aromatic dicarboxylic acids and aliphatic dihydroxy compounds, iv) 0.1 to 2% w/w, in relation to the total weight of components i to iv, of a copolymer containing epoxide groups based on styrene, acrylic ester and/or methacrylic ester, and v) 0 to 10% w/w, in relation to the total weight of components i to v, of one or a more additives; b) mixing vi) 3 to 7% w/w, in relation to the total weight of components i to v, of an organic expanding agent into the polymer melt using a static or dynamic mixer at a temperature of at least 140°C; c) discharging the melt through a nozzle plate with bores, the diameter of which at the exit from the nozzle is no greater than 1.5 mm; and d) granulating the melt containing the expanding agent directly downstream of the nozzle plate under water at a pressure ranging from 1 to 30 bar.

Description

Process for the preparation of expandable polylactic acid containing granules

The invention relates to a process for the preparation of expandable polylactic acid-containing granules, comprising the steps of: a) melting and mixing in the components i) 61, 9 to 98.9% by weight, based on the total weight of components i to iv, Polylactic acid, ii) from 1 to 38% by weight, based on the total weight of components i to iv, of at least one polyhydroxyalkanoate, iii) from 0 to 30% by weight, based on the total weight of components i to iv, at least one polyester based on aliphatic and / or aromatic dicarboxylic acids and aliphatic dihydroxy compounds; iv) from 0.1 to 2% by weight, based on the total weight of components i to iv, of an epoxide group-containing copolymer based on styrene, acrylic ester and / or methacrylic ester and v) 0 to 10% by weight, based on the Total weight of components i to v, one or more additives, b) mixing vi) 3 to 7 wt .-% based on the components i to v) of an organic blowing agent in the polymer melt by means of a static or dynamic mixer at a temperature of at least 140 ° C, c) discharge through a nozzle plate with holes whose diameter at the nozzle outlet is at most 1.5 mm and d) granulating the blowing agent-containing melt directly behind the nozzle plate under water at a pressure in the range of 1 to 30 bar.

Furthermore, the invention relates to expandable polylactic acid-containing granules obtainable by this process and special expandable polylactic acid-containing granules with a proportion of 3 to 7 wt .-% of an organic blowing agent, preferably iso-pentane. Furthermore, the invention relates to a preferred process for the preparation of propellant-containing, expandable polylactic acid-containing granules by underwater granulation at low temperatures or using an inert co-propellant. Finally, the invention relates to blowing agent-containing (expandable) granules which are accessible by means of the abovementioned processes.

Processes for the production of expandable granules which, in addition to polylactic acid, contain an aliphatic-aromatic polyester are known from WO 01/012706 and WO 201 1/086030. However, these granules can not always be fully satisfactory in terms of degradation under anaerobic conditions.

Expandable polylactic acid-containing granules containing polyhydroxyalkanoates (component ii) are not described in the literature. From EP 2168993 are only expanded Particle foams known, but based on compounds containing about 70 to 80 wt .-% polyhydroxyalkanoate and only 20 to 30 wt.% - Polylactic acid. In order to obtain particle foams with acceptable densities, several percent of a polyurethane compound must be added to the compounds before the foaming process, which in turn has a negative effect on the biodegradability. In addition, premature frothing of the granules can not be avoided in this process.

The object of the present invention was to provide a simple, process-capable process for the preparation of expandable polylactic acid-containing granules which decompose excellently under anaerobic conditions such as in a dry environment.

Accordingly, the method described above was found.

The process according to the invention is described in more detail below.

The polylactic acid-containing mixture used in step a) generally consists of: i) 61, 9 to 98.9% by weight, based on the total weight of components i to iv, of polylactic acid, ii) From 1 to 38% by weight, based on the total weight of components i to iv, of at least one polyhydroxyalkanoate, iii) from 0 to 30% by weight, based on the total weight of components i to iv, of at least one polyester based on aliphatic and / or aromatic dicarboxylic acids and aliphatic dihydroxy compounds; iv) 0.1 to 2% by weight, based on the total weight of components i to iv, of an epoxy group-containing copolymer based on styrene, acrylic ester and / or methacrylic acid ester, and v) 0 to 10% by weight. %, based on the total weight of components i to v, of one or more additives.

Preferably, the polylactic acid-containing mixture consists of i) 65 to 95 wt .-%, particularly preferably 70 to 90 wt .-% based on the total weight of components i to iv, polylactic acid, ii) 1 to 38 wt .-%, in particular From 10 to 30% by weight, based on the total weight of components i to iv, of at least one polyhydroxyalkanoate, iii) 0 to 30% by weight, particularly preferably 5 to 20% by weight, based on the total weight of components i to iv, of at least one polyester based on aliphatic dicarboxylic acids and aliphatic dihydroxy compounds or on polyalkylene succinate-co-terephthalate, iv) 0.1 to 2 wt .-%, particularly preferably 0.1 to 1 wt .-% based on the total weight of components i to iv, of an epoxide group-containing copolymer based on styrene, acrylic acid ester and / or methacrylic acid ester, and v) 0.1 up to 2% by weight, based on the total weight of components i to v, of a nucleating agent.

As component i), polylactic acid having the following property profile is preferably used:

A melt volume rate (MVR at 190 ° C. and 2.16 kg according to ISO 1133) of from 0.5 to 15, preferably from 1 to 9, particularly preferably from 5 to 8 ml / 10 minutes

• a melting point below 180 ° C;

· A glass point (Tg) greater than 40 ° C

• a water content of less than 1000 ppm

• a residual monomer content (lactide) of less than 0.3%.

• a molecular weight greater than 50,000 daltons. Examples of preferred polylactic acids of NatureWorks® are Ingeo® 2002 D, 4032 D, 4042 D and 4043 D, 8251 D, 3251 D and in particular 8051 D and 8052D. NatureWorks 8051D and 8052D are polylactic acids from NatureWorks, with the following product properties: Tg: 65.3 ° C, Tm: 153.9 ° C, MVR: 6.9 [ml / 10 minutes], M _w : 186000 , Mn: 107000. Furthermore, these products have a slightly higher acid number.

For the production of the expandable granules according to the invention, in particular polylactic acids having an MVR according to ISO 1 133 [190 ° C./2.16 kg] of 5 to 8 ml / 10 minutes have proven to be advantageous. Particularly suitable are polylactic acids, the o.g. Have MVR range and / or an onset temperature in the cold crystallization in the range of 80 ° C to 125 ° C, preferably at 90 ° C to 1 15 ° C and particularly preferably at 95 ° C to 105 ° C, measured by DSC (differential scanning calorimetry) at a heating rate of 20K / min (measuring range -60 ° C to 220 ° C; Mettler DSC 30 with a TC15 / TA controller, Mettler-Toledo AG).

It was found that most of the polylactic acid types available on the market under the conditions mentioned above an onset temperature in the cold crystallization of below 80 ° C. exhibit. A comparison of the polylactic acid (PLA) types NatureWorks® 8051 D, 8052D and 4042D is intended to clarify the different crystallisation behavior of the granulates produced therefrom (see table). The table shows DSC measurements of expandable granules of two types of PLA, each nucleated with 0.3% by weight of talc and loaded with 5.7% by weight of n-pentane propellant.

Table: DSC data at a heating rate of 20K / min (measuring range -60 ° C to 220 ° C)

The expandable granules generally have a crystalline content of only a few percent after preparation; So they are mostly amorphous. An increased onset temperature in the cold crystallization in the range of 80 ° C to 125 ° C, preferably at 90 ° C to 1 15 ° C and particularly preferably at 95 ° C to 105 ° C favors a foaming with water vapor. Crystallization and foaming behavior of the expandable granules are optimally matched to each other in PLA types such as NatureWorks® 8051 D, 8052D.

Polyhydroxyalkanoates (component ii) are understood as meaning primarily poly-4-hydroxybutyrates and poly-3-hydroxybutyrates and copolyesters of the abovementioned polyhydroxybutyrates with 3-hydroxyvalerate, 3-hydroxyhexanoate and / or 3-hydroxyoctanoate. Poly-3-hydroxybutyrates are sold, for example, by PHB Industrial under the brand name Biocycle® and by Tianan under the name Enmat®.

Poly-3-hydroxybutyrate-co-4-hydroxybutyrates are known in particular from Metabolix. They are sold under the trade name Mirel®.

Poly-3-hydroxybutyrate-co-3-hydroxyhexanoates are known, for example, from the company Kaneka. Poly-3-hydroxybutyrate-co-3-hydroxyhexanoates generally have one

3-Hydroxyhexanoatanteil of 1 to 20 and preferably from 3 to 15 mol% based on the component ii. Particularly preferred is a 3-hydroxyhexanoate content of 10 to 13 mol%. Poly-3-hydroxybutyrate-co-3-hydroxyhexanoates are particularly preferred for the particle foams of the invention.

The polyhydroxyalkanoates generally have a molecular weight Mw of from 100,000 to 1,000,000, and preferably from 300,000 to 600,000.

As component iii are aliphatic or partially aromatic (aliphatic-aromatic) to understand polyester. As component iii), as mentioned, purely aliphatic polyesters are suitable. Among aliphatic polyesters are polyesters of aliphatic C 2 -C 12 -alkanediols and aliphatic C 4 -C 36 -alkanedicarboxylic acids such as polybutylene succinate (PBS), polybutylene adipate (PBA), polybutylene succinate adipate (PBSA), polybutylene succinate sebacate (PBSSe), polybutylene sebacate adipate (PBSeA), polybutylene sebacate (PBSe ) or corresponding polyesteramides understood. The aliphatic polyesters are marketed by Showa Highpolymers under the name Bionolle and by Mitsubishi under the name GSPIa. More recent developments are described in WO 2010/03471 1.

The aliphatic polyesters generally have viscosity numbers according to DIN 53728 of 150 to 320 cm ³ / g and preferably 150 to 250 cm ³ / g.

MVR (melt volume rate) according to EN ISO 1133 (190 ° C, 2.16 kg weight) in general mean is 0.1 to 70, preferably from 0.8 to 70 and in particular from 1 to 60 cm ^3/10 minute

The acid numbers according to DIN EN 12634 are generally from 0.01 to 1.2 mg KOH / g, preferably from 0.01 to 1.0 mg KOH / g and particularly preferably from 0.01 to 0.7 mg KOH / g , Partaromatic polyesters which are also suitable as component iii) consist of aliphatic diols and aliphatic and aromatic dicarboxylic acids. Suitable partially aromatic polyesters include linear non-chain extended polyesters (WO 92/09654). In particular, aliphatic / aromatic polyesters of butanediol, terephthalic acid and aliphatic C4-C8 dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid and brassylic acid (for example as described in WO 2006/097353 to 56) are suitable mixing partners. Chain-extended and / or branched partially aromatic polyesters are preferably used as component iii. The latter are known from the aforementioned documents WO 96/15173 to 15176, 21689 to 21692, 25446, 25448 or WO 98/12242, to which reference is expressly made. Mixtures of different partly aromatic polyesters are also possible.

Biodegradable, aliphatic-aromatic polyesters iii which contain a) from 40 to 70 mol%, based on the components a to b, of one or more dicarboxylic acid derivatives or dicarboxylic acids selected from among the following are suitable for the process according to the invention for producing particle foams Group consisting of: succinic acid, adipic acid, sebacic acid, azelaic acid and brassylic acid; b) 60 to 30 mol%, based on components a to b, of a terephthalic acid derivative; c) 98 to 102 mol%, based on the components a to b, of a C2-C8-alkylenediol or C2-C6-oxyalkylenediol; d) 0.00 to 2 wt .-%, based on the total weight of components a to c, of a chain extender and / or crosslinker selected from the group consisting of: a di or polyfunctional isocyanate, isocyanurate, oxazoline, epoxy, peroxide, carbon acid anhydride and / or an at least trifunctional alcohol or an at least trifunctional carboxylic acid; suitable. Preferably used aliphatic-aromatic polyesters iii contain: a) 50 to 65 and in particular 58 mol%, based on components a to b, of one or more dicarboxylic acid derivatives or dicarboxylic acids selected from the group consisting of succinic acid, azelaic acid, brassylic acid and preferably adipic acid, in particular preferably sebacic acid; b) 50 to 35 and in particular 42 mol%, based on components a to b, of a terephthalic acid derivative; c) 98 to 102 mol%, based on the components a to b, 1, 4-butanediol and d) 0 to 2 wt .-%, preferably 0, 01 to 2 wt .-%, based on the total weight of components a to c, a chain extender and / or crosslinker selected from the group consisting of: a polyfunctional isocyanate, isocyanurate, oxazoline, carboxylic acid anhydride such as maleic anhydride, epoxide (in particular an epoxide-containing

Poly (meth) acrylate) and / or an at least trifunctional alcohol or an at least trifunctional carboxylic acid.

As aliphatic dicarboxylic acids are preferably succinic acid, adipic acid and particularly preferably sebacic acid. Succinic and sebacic acid-containing polyesters have the advantage that they are also available as a renewable raw material.

Preferably used polyesters iii contain: a) 90 to 99.5 mol%, based on the components a to b, succinic acid; b) 0.5 to 10 mol%, based on the components a to b, one or more

C8-C20 dicarboxylic acids c) 98 to 102 mol%, based on the components a to b, 1, 3-propanediol or

1, 4-butanediol. Particularly preferably used polyesters iii contain: a) 90 to 99.5 mol%, based on the components a to b, succinic acid; b) 0.5 to 10 mol%, based on the components a to b, terephthalic acid, azelaic acid, sebacic acid and / or brassylic acid c) 98 to 102 mol%, based on the components a to b, 1, 3-propanediol or 1 , 4-butanediol and d) 0.01 to 5 wt .-%, based on the total weight of components a to c, of a chain extender and / or crosslinker selected from the group consisting of: a polyfunctional isocyanate, isocyanurate, oxazoline, epoxy ( in particular an epoxy-containing poly (meth) acrylate), an at least trifunctional alcohol or an at least trifunctional carboxylic acid.

The polyesters iii generally have a number average molecular weight (Mn) in the range from 5000 to 100,000, in particular in the range from 10,000 to 75,000 g / mol, preferably in the range from 15,000 to 38,000 g / mol, a weight average molecular weight (Mw) of 30,000 to 300,000, preferably 60000 to 200,000 g / mol and a Mw / Mn ratio of 1 to 6, preferably 2 to 4 on. The viscosity number is between 50 and 450, preferably from 80 to 250 g / ml (measured in o-dichlorobenzene / phenol (weight ratio 50/50).) The melting point is in the range of 85 to 150, preferably in the range of 95 to 140 ° C. The abovementioned polyesters can have hydroxyl and / or carboxyl end groups in any desired ratio. [Te Die] The partially aromatic polyesters can also be end-group-modified, for example OH end groups can be obtained by reaction with phthalic acid, phthalic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid or pyromel polyesters with acid numbers of less than 1.5 mg KOH / g are preferred.

Component iv) is described in more detail below.

Epoxides are understood as meaning, in particular, epoxide-group-containing copolymer based on styrene, acrylic acid ester and / or methacrylic acid ester. The epoxy groups bearing units are preferably glycidyl (meth) acrylates. Copolymers having a glycidyl methacrylate content of greater than 20, particularly preferably greater than 30 and especially preferably greater than 50% by weight, of the copolymer have proven to be advantageous. The epoxy equivalent weight (EEW) in these polymers is preferably 150 to 3000, and more preferably 200 to 500 g / equivalent. The weight average molecular weight Mw of the polymers is preferably from 2,000 to 25,000, in particular from 3,000 to 8,000. The number average molecular weight M _{n of} the polymers is preferably from 400 to 6,000, in particular 1,000 up to 4,000. The polydispersity (Q) is generally between 1 .5 and 5 epoxide groups-containing copolymers of the above type are sold for example by BASF Resins BV under the trademark Joncryl ^® ADR. Particularly suitable as component iv) is Joncryl ^® ADR 4368th

Component v is understood in particular to be one or more of the following additives: stabilizer, nucleating agent, lubricants and release agents, such as stearates (in particular calcium stearate); Plasticizers such as citric acid esters (especially acetyl tributyl citrate), glyceric acid esters such as triacetylglycerol or ethylene glycol derivatives, surfactants such as polysorbates, palmitates or laurates; Waxes such as beeswax or bee wax esters; Antistatic, UV absorber; UV-stabilizer; Antifog agents, dyes, fillers or other plastic additives. The additives are used in concentrations of from 0 to 10% by weight, in particular from 0.1 to 2% by weight, based on the polyesters according to the invention. As already mentioned, the use of 0.5 to 1% by weight, based on the components i to v of a nucleating agent, is particularly preferred.

Nucleating agent is understood in particular to be talc, chalk, carbon black, graphite, calcium or zinc stearate, poly-D-lactic acid, N, N'-ethylene-bis-12-hydroxystearamide or polyglycolic acid. Talcum is particularly preferred as nucleating agent.

The propellant can be considered as a further component vi.

The blowing agent-containing polymer melt generally contains one or more blowing agents in a homogeneous distribution in a proportion of 3 to 7 wt .-%, based on the blowing agent-containing polymer melt. When using co-blowing agents vii less than 3 wt .-% blowing agent vi can be used. Suitable blowing agents are the physical blowing agents commonly used in EPS, such as aliphatic hydrocarbons having 2 to 7 carbon atoms, alcohols, ketones, ethers, amides or halogenated hydrocarbons. Preference is given to using isobutane, n-butane, n-pentane and, in particular, isopentane. Further preferred are mixtures of n-pentane and iso-pentane and of n-butane and iso-pentane.

The amount of blowing agent added is chosen such that the expandable granules have an expansion capacity a, defined as bulk density before pre-foaming of 500 to 800 and preferably 580 to 800 kg / m ³ and a bulk density after pre-foaming of at most 125, preferably 8 to 100 kg / m ³ have.

When using fillers, depending on the type and amount of the filler, bulk densities in the range of 590 to 1200 kg / m ³ may occur. To prepare the expandable granules according to the invention, the blowing agent is mixed into the polymer melt. The process comprises the stages a) melt production, b) mixing c) conveying and d) granulating. Each of these steps can be processing known apparatus or apparatus combinations are performed. For mixing, static or dynamic mixers are suitable, for example extruders. The polymer melt can be produced directly by melting polymer granules. If necessary, the melt temperature can be lowered via a cooler. For example, pressurized underwater granulation, granulation with rotating knives and cooling by spray misting of tempering liquids come into consideration for the granulation. Apparatus arrangements suitable for carrying out the method are, for example: i) extruder - static mixer - cooler - granulator

ii) extruder - granulator

Furthermore, the arrangement may include a side extruder for introducing additives, e.g. of solids or thermally sensitive additives. The propellant-containing polymer melt is usually conveyed through the nozzle plate at a temperature in the range from 140 to 300.degree. C., preferably in the range from 160 to 240.degree.

The nozzle plate is heated at least to the temperature of the propellant-containing polymer melt. Preferably, the temperature of the nozzle plate is in the range of 20 to 100 ° C above the temperature of the propellant-containing polymer melt. This prevents polymer deposits in the nozzles and ensures trouble-free granulation.

In order to obtain marketable granule sizes, the diameter (D) of the nozzle bores at the nozzle exit should be in the range from 0.1 to 2 mm, preferably in the range from 0.1 to 1.2 mm, particularly preferably in the range from 0.1 to 0 , 8 mm lie. This granulate sizes below 2 mm, especially in the range 0.2 to 1, 4 mm can be adjusted specifically after strand expansion.

The strand expansion can be influenced by the nozzle geometry, as well as the molecular weight distribution. The nozzle plate preferably has bores with a ratio L / D of at least 2, the length (L) designating the nozzle region whose diameter corresponds at most to the diameter (D) at the nozzle exit. Preferably, the ratio L / D is in the range of 3 - 20. In general, the diameter (E) of the holes at the nozzle entrance of the nozzle plate should be at least twice as large as the diameter (D) at the nozzle exit.

An embodiment of the nozzle plate has bores with conical inlet and an inlet angle α less than 180 °, preferably in the range of 30 to 120 °. In a further embodiment, the nozzle plate has bores with a conical outlet and an outlet angle β of less than 90 °, preferably in the range of 15 to 45 °. In order to produce specific granule size distributions of the polymers, the nozzle plate can be provided with bores of different exit diameters. be equipped knife (D). The various embodiments of the nozzle geometry can also be combined.

A preferred process for preparing expandable polylactic acid-containing granules comprises the steps of a) melting and mixing in the components i) 61, 9 to 98.9% by weight, based on the total weight of components i to iv, polylactic acid, ii) from 1 to 38% by weight, based on the total weight of components i to iv, of at least one polyhydroxyalkanoate, iii) from 0 to 30% by weight, based on the total weight of components i to iv, of at least one polyester Base of aliphatic and / or aromatic dicarboxylic acids and aliphatic dihydroxy compounds; iv) from 0.1 to 2% by weight, based on the total weight of components i to iv, of an epoxide group-containing copolymer based on styrene, acrylic ester and / or methacrylic ester and v) 0 to 10% by weight, based on the Total weight of components i to v, of one or more additives, b) incorporation of an organic blowing agent in the polymer melt, if appropriate by means of a static or dynamic mixer at a temperature of at least 140 ° C., preferably 180-260 ° C., if appropriate the blowing agent-containing polymer melt c) discharged through a nozzle plate with holes whose diameter at the nozzle outlet is at most 1, 5 mm and d) granulating the blowing agent-containing melt directly behind the nozzle plate below Water at a pressure in the range of 1 to 20 bar.

Furthermore, it was found that a lowering of the temperature in the underwater granulation to 5 to 20 ° C to expandable polylactic acid-containing granules with defined

Voids having a mean diameter in the range of 0.1 to 50 μηη leads. In general, the granules have an average diameter in the range of 0.1 to 2 mm and 50 to 300 cavities / mm ² cross-sectional area. By lowering the temperature of underwater granulation, the bulk density can be reduced to the range of 580 to 800 kg / m ³ and preferably 580 to 720 kg / m ³ . Furthermore, the expandable polylactic acid-containing granules thus produced have an increased storage stability. They can be foamed easily after weeks.

The reduction in the bulk density and increase in the storage stability of the expandable polylactic acid-containing granules can also be achieved with the following preferred procedure: a) melting and mixing the components i) 61, 9 to 98.9 wt .-%, based on the total weight of components i to iv, polylactic acid, ii) 1 to 38 wt .-%, based on the total weight of the components i to iv, at least one polyhydroxyalkanoate, iii) 0 to 30% by weight, based on the total weight of components i to iv, of at least one polyester based on aliphatic and / or aromatic dicarboxylic acids and aliphatic dihydroxy compounds; iv) 0.1 to 2 wt .-%, based on the total weight of components i to iv, of an epoxy group-containing copolymer based on styrene, acrylic acid ester and / or methacrylic acid ester and v) 0.1 to 5 wt .-%, based on the total weight of the components i to v, of a nucleating agent,

Mixing vi) from 1 to 7% by weight, based on the total weight of components i to v, of an organic blowing agent; and vii) from 0.01 to 5% by weight of a co-blowing agent selected from the group consisting of nitrogen, carbon dioxide, argon , Helium or mixtures thereof - in the polymer melt optionally by means of a static or dynamic mixer at a temperature of at least 140 ° C,

Discharge through a nozzle plate with holes whose diameter at the nozzle outlet is at most 1, 5 mm and

Granulating the blowing agent-containing melt directly behind the nozzle plate under water at a pressure in the range of 1 to 20 bar.

By the use of volatile, liquid / gaseous cavities forming co-propellants vii) a cellular structure can be adjusted in the expandable granules, with the help of which the subsequent foaming process can be improved and the cell size can be controlled.

As nucleating agent v) and propellant vi), the agents described above are suitable.

The method for adjusting this cavity morphology may also be referred to as pre-nucleation, the cavities being formed essentially by the co-propellant vii).

The cavities forming co-propellant vii) differs from the actual propellant vi in its solubility in the polymer. In the preparation of the first propellant vi) and co-propellant vii) are completely dissolved in the polymer at sufficiently high pressure. Subsequently, the pressure is reduced, preferably within a short time, and thus reduces the solubility of the co-propellant vii). This results in a phase separation in the polymeric matrix and a vorukleierter structure arises. The actual propellant vi) remains largely dissolved in the polymer due to its higher solubility and / or its low diffusion rate. Simultaneously with the pressure reduction, a temperature reduction is preferably carried out in order to prevent excessive nucleation of the system and to prevent out-diffusion. ren of the actual propellant vi) to reduce. This is achieved by co-propellant vii) in conjunction with optimum granulation conditions.

Preferably, the co-propellant vii) escapes to at least 80 wt .-% within 24 h of the expandable thermoplastic particles when stored at 25 ° C, atmospheric pressure and 50% relative humidity. The solubility of the co-blowing agent vii) in the expandable thermoplastic particles is preferably below 0.1 wt .-%.

In all cases, the added amount of co-propellant vii) used in the pre-nucleation should exceed the maximum solubility at the present process conditions. Therefore, preference is given to using co-blowing agents vii) which have a low but sufficient solubility in the polymer. These include in particular gases such as nitrogen, carbon dioxide, air or noble gases, more preferably nitrogen, whose solubility in many polymers is reduced at low temperatures and pressures. But there are also other liquid additives conceivable.

Particular preference is given to using inert gases such as nitrogen and carbon dioxide. In addition to their suitable physical properties, both gases are distinguished by low costs, good availability, easy handling and inert or inert behavior. For example, in the presence of the two gases, in almost all cases, no degradation of the polymer takes place. Since the gases themselves are extracted from the atmosphere, they also have an environmentally neutral behavior.

The amount of co-propellant vii) used should be: (a) sufficiently small to dissolve at the given melt temperatures and pressures during melt impregnation until granulation; (b) be sufficiently high to segregate and nucleate at the granulation water pressure and granulation temperature from the polymer. In a preferred embodiment, at least one of the blowing agents used is gaseous at room temperature and under atmospheric pressure.

Particular preference is given to using talc as nucleating agent v) in combination with nitrogen as co-blowing agent vii).

Metallic barrels and octabins are used, among other things, for the transport and storage of the expandable granules. When using barrels, it should be noted that the release of the co-propellants vii) may possibly build up pressure in the drum. As packaging, therefore, preferably open containers such as octabins or barrels are to be used, which allow a pressure reduction by permeation of the gas from the barrel. Drums which allow the co-propellant vii) to diffuse out and minimize or prevent the actual propellant vi) from being discharged are particularly preferred. This can be made possible for example by the vote of the sealing material on the blowing agent or co-blowing agent vii). Preferably, the permeability of the sealing material for the co-propellant mean vii) at least a factor of 20 higher than the permeability of the sealing material for the propellant vi).

By Vornukleierung, for example, by adding small amounts of nitrogen and carbon dioxide, a cellular morphology can be adjusted in the expandable, propellant-containing granules. The mean cell size in the center of the particles can be greater than in the edge regions, the density in the edge regions of the particles higher. As a result, blowing agent losses are minimized as much as possible. By Vornukleierung a significantly better cell size distribution and a reduction of the cell size after pre-foaming can be achieved. In addition, the required amount of blowing agent to achieve a minimum bulk density is lower and the storage stability of the material is improved. Small amounts of nitrogen or carbon dioxide when added to the melt can lead to a significant shortening of the prefoaming at a constant blowing agent content or to a significant reduction in blowing agent quantities with constant foaming times and minimum foam densities. In addition, the pre-nucleation improves product homogeneity and process stability.

Further impregnation of the polymer granules according to the invention with blowing agents is furthermore possible much faster than with granules of identical composition and more compact, ie. H. noncellular structure. On the one hand, the diffusion times are lower, on the other hand, it requires analogous to directly impregnated systems lower blowing agent amounts for foaming. Finally, by Vornukleierung the blowing agent content, which is required to achieve a certain density is reduced, and thus the demolding times in the molding or block production can be reduced. Thus, the processing costs can be reduced and the product quality can be improved. The principle of pre-nucleation can be used both for suspension technology and for melt impregnation technology for the production of expandable particles. Preference is given to the use in the melt extrusion process, in which the addition of the co-blowing agent vii) with the blowing agents vi) takes place in step b and finally granulated by the pressure-assisted underwater granulation after the blowing agent-laden melt. By selecting the granulation parameters and the co-propellant vii), the microstructure of the granules can be controlled as described above.

For higher amounts of co-propellant vii), for example in the range of 1 to 10 wt .-% based on the propellant-containing polymer melt, a lowering of the melt temperature or the melt viscosity and thus a significant increase in throughput is possible. Thus, a gentle incorporation of thermolabile additives, such as flame retardants, the polymer melt is possible. The composition of the expandable thermoplastic Particles are not altered as a result of the fact that the co-blowing agent essentially escapes during melt extrusion. To utilize this effect, CO2 is preferably used. At N2 the effects on the viscosity are lower. Nitrogen is therefore used predominantly to set the desired cell structure.

The liquid-filled chamber for granulating the expandable thermoplastic polymer particles is preferably operated at a temperature in the range of 20 to 80 ° C, more preferably in the range of 30 to 60 ° C. In order to keep the thermal degradation of the polylactic acid as low as possible, it is also appropriate to keep the mechanical and thermal energy input in all process stages as low as possible. The mean shear rates in the screw channel should be low, shear rates below 250 / sec, preferably below 100 / sec, and temperatures below 260 ° C. and short residence times in the range from 2 to 10 minutes in stages c) and d) are preferably maintained , The residence times are without cooling step usually at 1, 5 to 4 minutes and when a cooling step is provided usually at 5 to 10 minutes. The polymer melt can by pressure pumps, z. B. gear pumps funded and discharged.

To improve processability, the finished expandable granules may be coated by glycerol esters, antistatic agents or anticaking agents.

The expandable granules according to the invention have a lower bond to granules containing low molecular weight plasticizers, and are characterized by a low pentane loss during storage.

The expandable granules according to the invention can be prefoamed in a first step by means of hot air or steam to foam particles having a density in the range of 8 to 100 kg / m ³ and welded in a second step in a closed mold to particle moldings.

Surprisingly, the foam beads have a significantly higher crystallinity than the expandable granules. The crystallinity can be determined by means of small angle Xray scattering (or SAXS analysis for short). The expandable granules generally have a crystalline content of only a few percent after production - ie are predominantly amorphous - while the foamed beads have a significantly higher crystallinity of 8 to 40% and thus a significantly higher heat resistance

The granules produced by the process according to the invention have a high biological degradability and good properties during foaming. For the purposes of the present invention, the feature "biodegradable" for a substance or a substance mixture is fulfilled if this substance or the substance mixture according to DIN EN 13432 has a percentage degree of biodegradation of at least 90%. The particle foams according to the invention have a higher degradability, especially under anaerobic conditions.

In general, biodegradability causes the granules or foams made therefrom to decay within a reasonable and detectable period of time. The decomposition can be effected enzymatically, hydrolytically, oxidatively and / or by the action of electromagnetic radiation, for example UV radiation, and for the most part be effected for the most part by the action of microorganisms such as bacteria, yeasts, fungi and algae. The biodegradability can be quantified, for example, by mixing polyesters with compost and storing them for a certain period of time. For example, according to DIN EN 13432, C02-free air is allowed to flow through matured compost during composting. The compost is subjected to a defined temperature program. Here, the biodegradability is determined by the ratio of the net CO 2 release of the sample (after deduction of CO 2 release by the compost without sample) to the maximum CO 2 release of the sample (calculated from the carbon content of the sample) as a percentage of biodegradation Are defined. Biodegradable granules usually show after a few days of composting significant degradation phenomena such as fungal growth, crack and hole formation.

Other methods of determining biodegradability are described, for example, in ASTM D 5338 and ASTM D 6400-4.

Examples

Materials used: Component i: i-1: aliphatic polyester, polylactide NatureWorks ^® 8051 D from Nature Works..

Component ii: ii-1 Poly-3-hydroxybutyrate-co-3-hydroxyhexanoate with 1 1% hexanoate comonomer fraction from Kaneka (trade name Aonilex).

Component iii: iii- 1: To prepare the polyester ii-2 were used in a 450 liter polycondensation kettle

14.89 kg sebacic acid, 165.18 kg succinic acid, 172.5 kg 1, 4-butanediol and 0.66 kg glycerol together with 0.031 kg tetrabutyl orthotitanate (TBOT) mixed, the molar ratio between alcohol components and acid component being 1.30. The reaction mixture was heated to an internal temperature of 200 ° C. while distilling off water and kept at this temperature for 1 h. Subsequently, the temperature was increased to an internal temperature of about 250-260 ° C and at the same time distilled off the excess 1, 4-butanediol under application of vacuum (final vacuum about 3-20 mbar). The polycondensation was stopped after reaching the desired final viscosity by cooling to about 180-200 ° C and the prepolyester with 1, 5 kg hexamethylene diisocyanate at 240 ° C for 1 h chain extended and granulated.

The thus-obtained polyester iii-1 had a molecular weight (Mn) of 37,000 g / mol. Component IV: IV-1: Joncryl ^® ADR 4368 CS from BASF SE.. Component v: v-1: HP 325 Chinatalk Luzenac Component vi: vi-1: Propellant: iso-pentane Component vii: vii-1: Co-propellant: Nitrogen (N ₂ )

The proportions correspond to% by weight and relate to 100% by weight of polymer (components i to v)

Example 1 :

4.9 parts of iso-pentane (component vi-1) and 0.1 part of nitrogen (vii-1) were added to a melt of 89.3 parts component i-1, 10 parts component ii-1, 0.3 parts component iv-1 and 0.4 parts of component v-1 mixed at a melt temperature of 160-240 ° C. The melt was conveyed at a rate of 4.5 kg / h through a die plate having a bore (diameter 0.65 mm). Using pressurized (15 bar) underwater granulation, compact (annuklierte / vorukleierte) granules were made with a narrow size distribution. The average particle size was 1.4 mm and the expandable granules had a density of 680 kg / m ³ .

The granules were prefoamed by the action of flowing steam. The foamed granules have a density of 36 kg / m ³ . The minimum bulk density of the foamed granule beads was still 53 kg / m ³ after 13 weeks.

Example 2:

4.9 parts of iso-pentane (component vi-1) and 0.1 part of nitrogen (vii-1) were added to a melt of 79.3 parts of component i-1, 20 parts of component ii-1, 0.3 parts of com Component iv-1 and 0.4 part of component v-1 are mixed at a melt temperature of 160-240 ° C.

The melt was conveyed at a rate of 4.5 kg / h through a die plate having a bore (diameter 0.65 mm). Using pressurized (15 bar) underwater granulation, compact (annuklierte / vorukleierte) granules were made with a narrow size distribution. The average particle size was 1.4 mm and the expandable granules had a density of 695 kg / m ³ .

The granules were prefoamed by the action of flowing steam. The foamed granules have a density of 53 kg / m ³ . The minimum bulk density of the foamed granule beads was still 68 kg / m ³ after 13 weeks.

Example 3: 4.9 parts of iso-pentane (component vi-1) and 0.1 part of nitrogen (vii-1) were in a

Melt of 69.3 parts component i-1, 30 parts component ii-1, 0.3 parts component iv-1 and 0.4 parts component v-1 mixed at a melt temperature of 160-240 ° C. The melt was conveyed at a rate of 4.5 kg / h through a die plate having a bore (diameter 0.65 mm). Using pressurized (15 bar) underwater granulation, compact (annuklierte / vorukleierte) granules were made with a narrow size distribution. The average particle size was 1.4 mm and the expandable granules had a density of 725 kg / m ³ . The granules were prefoamed by the action of flowing steam. The foamed granules have a density of 65 kg / m ³ . The minimum bulk density of the foamed granule beads was still 85 kg / m ³ after 13 weeks. Example 4:

4.9 parts of isopentane (component vi-1) and 0.1 part of nitrogen (vii-1) were dissolved in a melt of 59.3 parts of component i-1, 30 parts of component ii-1, 10 parts of component iii. 1, 0.3 parts of component iv-1 and 0.4 parts of component v-1 mixed at a melting temperature of 160-240 ° C.

The melt was conveyed at a rate of 4.5 kg / h through a die plate having a bore (diameter 0.65 mm). Using pressurized (15 bar) underwater granulation, compact (annuklierte / vorukleierte) granules were produced with a narrow size distribution. The average particle size was 1.4 mm and the expandable granules had a density of 750 kg / m ³ .

The granules were prefoamed by the action of flowing steam. The foamed granules have a density of 140 kg / m ³ . The minimum bulk density of the foamed granule beads was still 286 kg / m ³ after 13 weeks.

Comparative Example 5:

4.9 parts of iso-pentane (component vi-1) and 0.1 part of nitrogen (vii-1) were added to a melt of 59.3 parts component i-1, 40 parts component ii-1, 0.3 parts component iv-1 and 0.4 parts of component v-1 are mixed at a melt temperature of 160-240 ° C.

The melt was conveyed at a rate of 4.5 kg / h through a nozzle plate with a bore (diameter 0.65 mm). Using pressurized (15 bar) underwater granulation, compact (annuklierte / vorukleierte) granules were made with a narrow size distribution. The average particle size was 1.4 mm and the expandable granules had a density of 745 kg / m ³ . The granules were prefoamed by the action of flowing steam. The foamed granules have a density of 218 kg / m ³ . The minimum bulk density of the foamed granule beads was still 551 kg / m ³ after 13 weeks.

Table 1 :

Example 1 Bsp-2 Bsp-3 Bsp-4 See Bsp-5

PLA / PHBH PLA / PHBH PLA / PHBH PLA / PHBH / PLA / PHBH PBSSe

Component i-1 89.3 79.3 69.3 59.3 59.3

Component ii-1 10 20 30 30 40

Component iii-1 0 0 0 10 0

Component iv-1 0.3 0.3 0.3 0.3 0.3

Component v-1 0.4 0.4 0.4 0.4 0.4

Component vi-1 4.9 4.9 4.9 4.9 4.9

Component vii-1 0.1 0.1 0.1 0.1 0.1

Minimum bulk density

680 695 725 750 745

granules

(Kg / m3)

Minimum bulk density foam,

36 53 65 140 218 directly after production (kg / m3)

Minimum bulk density foam

53 68 85 286 551 after 13 weeks

(Kg / m3)

The results in Table 1 clearly show that as the proportion of polyhydroxyalkanoate increases, the crystallinity of expandable granules and, in particular, also of the foamed granule beads, increases.

If the proportion of polyhydroxyalkanoate is too high (component ii above 30% by weight), foamed granulated beads of low density can no longer be produced (see Comparative Example 5). Surprisingly, this effect is not so pronounced when using polylactic acid-containing polymers which additionally contain from 1 to 29.9% by weight of an aliphatic or partly aromatic polyester (component iii) (Example 4) than in the case of a polylactic acid-containing polymer, which has no component iii.

Table 2: Crystallinity measured by SAXS analysis

Crystallinity granules (%) crystallinity foam bead (%)

Example 1 8

Example 4 13 17

Comp. Ex. 5 17 18

Claims

claims:

A process for the preparation of expandable polylactic acid-containing granules, comprising the steps of: a) melting and blending the components i) 61, 9 to 98.9 wt .-%, based on the total weight of components i to iv, polylactic acid, ii) 1 to 38% by weight, based on the total weight of components i to iv, of at least one polyhydroxyalkanoate, iii) 0 to 30% by weight, based on the total weight of components i to iv, of at least one aliphatic-based polyester and / or aromatic dicarboxylic acids and aliphatic dihydroxy compounds; iv) from 0.1 to 2% by weight, based on the total weight of components i to iv, of an epoxide-group-containing copolymer based on styrene, acrylic ester and / or methacrylic acid ester and v) 0 to 10% by weight, based on the Total weight of components i to v, one or more additives,

Mixing vi) 3 to 7% by weight, based on the total weight of components i to v, of an organic blowing agent into the polymer melt by means of a static or dynamic mixer at a temperature of at least 140 ° C.,

Discharge through a nozzle plate with holes whose diameter at the nozzle outlet is at most 1, 5 mm and d) granulating the blowing agent-containing melt directly behind the nozzle plate under water at a pressure in the range of 1 to 30 bar.

A method according to claim 1, characterized in that as component i) in step a) polylactic acid with an MVR to ISO 1 133 [190 ° C / 2.16 kg] of 5 to 8 ml / 10 minutes is used.

Process according to Claim 1, characterized in that the polyhydroxyalkanoate (component ii) used in stage a) is a poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) or a poly (3-hydroxybutyrate-co-4-hydroxybutyrate).

A method according to claim 1, characterized in that iso-pentane is used as the organic blowing agent in step b).

Process according to claims 1 to 4, characterized in that the underwater granulation is carried out at a temperature of 5 to 20 ° C.

Process for the preparation of expandable polylactic acid-containing granules, comprising the steps: a) melting and mixing the components i) 61, 9 to 98.9 wt .-%, based on the total weight of components i to iv, polylactic acid, ii) 1 to 38 wt .-%, based on the total weight of the components i to iv, at least one polyhydroxyalkanoate, iii) 0 to 30% by weight, based on the total weight of components i to iv, of at least one polyester based on aliphatic and / or aromatic dicarboxylic acids and aliphatic dihydroxy compounds; iv) 0.1 to 2 wt .-%, based on the total weight of components i to iv, of an epoxy group-containing copolymer based on styrene, acrylic acid ester and / or methacrylic acid ester and v) 0.1 to 5 wt .-%, based on the total weight of components i to v, of a nucleating agent, b) mixing in vi) 1 to 7% by weight, based on the total weight of components i to v, of an organic blowing agent and vii) 0.01 to 5 wt. -% of a co-propellant

- selected from the group of nitrogen, carbon dioxide, argon, helium or mixtures thereof - in the polymer melt by means of a static or dynamic mixer at a temperature of at least 140 ° C, c) discharge through a nozzle plate with holes whose diameter at the nozzle exit at most 1, 5 mm and d) granulating the blowing agent-containing melt directly behind the die plate under water at a pressure in the range of 1 to 30 bar.

A method according to claim 6, characterized in that the underwater granulation is carried out at 20 to 80 ° C.

Expandable polylactic acid-containing granules obtainable by a process according to claims 5 to 7, characterized in that they have a bulk density in the range of 580 to 800 kg / m ³ .

Expandable polylactic acid-containing granules, having a solids content of 93 to 97 wt .-% comprising: i) 61, 9 to 98.9 wt .-%, based on the total weight of components i to iv, polylactic acid, ii) 1 to 38 % By weight, based on the total weight of components i to iv, of at least one polyhydroxyalkanoate, iii) 0 to 30% by weight, based on the total weight of components i to iv, of at least one polyester based on aliphatic and / or aromatic dicarboxylic acids and aliphatic dihydroxy compounds; iv) 0.1 to 2 wt .-%, based on the total weight of components i to iv, one

Epoxy group-containing copolymer based on styrene, acrylic ester and / or methacrylic acid ester, and v) 0 to 10 wt .-%, based on the total weight of components i to v, of one or more additives; and an amount of from 3 to 7% by weight, based on the total weight of the components i to v, of an organic blowing agent. 10. A process for the production of particle foam moldings, characterized in that prefoamed expandable polylactic acid-containing granules according to claims 8 to 9 in a first step by means of hot air or steam to foam particles having a density in the range of 8 to 100 kg / m ³ and in welded in a second step in a closed mold.

1 1. Use of the expandable polylactic acid-containing granules according to claims 8 to 9 for the production of meat, sausage, and soup bowls, beverage cups, agro-articles, food packaging, electrical articles, for insulation in the construction industry and for shock and sound absorption ,