DE102008025697A1 - Thermoplastic molding mass for producing a molded part, comprises a matrix phase made of starch ester and plasticizer and containing nanoscale filler - Google Patents

Abstract

The thermoplastic molding mass comprises a matrix phase made of starch ester and plasticizer and containing nanoscale filler, where the starch ester has a degree of substitution of 2.1-2.9. The filler has cation-exchange capacity of 30-250 mval (milliequivalents) per 100 g. The weight portion of the matrix phase related to the molding mass is 99.9-80 wt.%. The weight portion of the nanoscale filler related to the molding mass is 2.5-7.5 wt.%. The weight portion of the plasticizer related to the molding mass is 15-25 wt.%. The nanoscale filler has average particle size (d 50) of 2-8 mu m. Independent claims are included for: (1) a method for producing a thermoplastic molding mass; (2) a molded part; and (3) a method for producing a molded part.

Description

The The present invention relates to a thermoplastic molding composition, the one matrix phase, the one starch ester and one Plasticizer comprises, as well as one homogeneously distributed in the matrix phase contains nanoscale filler.

Strength is one of the cheapest and most abundant renewable raw materials and has due to their polymeric structure Potential applications not only in the food sector, but also in food the polymer processing industry. In commercially available Products, eg B. Novamont, IT) will be existing, for Starch materials typical disadvantages, such as brittleness, Moisture sensitivity and tendency to stick due to patented Plasticizer, additives and co-components balanced.

however There is another way to gain strength in materials with beneficial to convert mechanical properties: the derivatization of Hydroxyl groups of the components amylose and amylopectin. Furthermore These derivatives can be used as matrix materials for Nanocomposites with z. B. phyllosilicates are used to further To achieve property improvements.

Various efforts to improve the properties of starch-based thermoplastic materials are described in the literature. In US 5,362,777 describes additives and plasticizers for producing thermoplastically processable starch, which bring the melting point of the starch below the decomposition point. These additives and plasticizers include dimethyl sulfoxides, various polyols, and amino and amide compounds. Improved plasticizers, ie substances that facilitate the destructuring of the starch, ie the dissolution of the starch granules and lower the corresponding temperatures, are known in WO 2005/090462 disclosed, wherein these are aldehyde group-containing hydrocarbon polymers. In US 5,043,196 For example, high amylose starch with an amylose content of at least 45% by weight is used as the starting material for foamed products for applications in particular in the packaging industry (loose fill).

A filled starch system, however, without the use of nanoscale fillers, is used in US 5,869,647 disclosed. The authors describe derivatized high amylose starch, more specifically starch propionate, which is compounded with a plasticizer such as glycerol or triacetin (glycerol triacetate) and talc as a filler. They achieve improved strengths and stiffnesses (Young moduli), but the elongation at break remains low and reaches at most 3%, the material is brittle. The only exception is the comparatively used system with 65% unmodified starch and 35% glycerol which reaches 6% elongation at 50% humidity but whose strengths and stiffnesses are extremely low at 0.8 MPa and 34 MPa.

In WO 2008/014573 Unmodified starch-based systems are described which cover a wide range of properties, but necessarily include a water-soluble, non-starch-based and thus significantly less favorable polymer, such as polyvinyl alcohol, polyvinyl acetate or ethylene vinyl alcohol. The fillers used are talc, wollastonite and amorphous and crystalline silicon dioxide.

The WO 01/68762 is concerned with biodegradable, especially starch-containing thermoplastic materials, wherein nanoscale exfoliated phyllosilicates are used in combination with water as a plasticizer. The authors find a stabilizing effect of the phyllosilicates which substantially prevent the drying out of the starch systems and the consequent increase in brittleness after deformation. However, these materials still have a poor elongation at break.

Maleated starch prepared by a reactive extrusion process, ie starch reacted with maleic acid or its anhydride, is dissolved in US 2006/0107945 disclosed. This is a starch derivative with a remaining carboxy group to which layer silicates can optionally be added, but whose influence on the properties is not stated.

With the molding compositions known from the prior art described above However, there are major disadvantages, especially the brittleness the starch ester based materials with sufficient strengths and stiffnesses for z. B. injection molding applications. So far could not realize any satisfactory solutions here become.

Thus, it is an object of the present invention to provide a starch ester-based thermoplastic molding composition, the lower brittleness and better processability in contrast to the prior art comprising materials known in the art.

These Task is with respect to the molding compound with the features of claim 1, relating to the method of manufacture the molding composition with the features of claim 11, with respect a produced from the molding composition according to the invention Molded part with the features of claim 14, with respect the method for producing the molded part with the features of Patent claim 17 and with regard to the purposes of use the moldings with the features of claim 18 solved. The respective dependent claims put thereby advantageous developments.

According to the invention thus a thermoplastic molding composition comprising a matrix phase from at least one starch ester and at least one Plasticizer provided, wherein in the matrix phase at least a nanoscale filler is included.

Surprisingly have molded bodies made from the invention Moldings were injection molded, a significantly increased Strength, a significantly increased module and at the same time a significantly increased elongation at break compared to moldings made of the same material without nanoscale sheet silicates. The latter is particularly surprising since usually the Elongation at break as a measure of toughness (Non-brittleness) when adding fillers (also nanoscale) sinks.

Especially is the starch ester selected from the group consisting of starch acetate, starch propionate, Starch butyrate and / or mixtures thereof.

The preferred degrees of substitution of the invention used Starch esters are between 1.4 and 3 substituted OH groups per sugar ring of strength. Especially preferred the degrees of substitution (DS) are between 2.1 and 2.9.

The Output strength can come from any source, z. As corn, wheat, tapioca, potato and may be different Relationships between amylose and amylopectin fractions exhibit. This ranges from virtually amylose-free starches, z. As waxy maize starch, up to hochamylosigen starches with Amylose contents above 50 wt .-%. The esterification is transferred the hydrophilic starch in a hydrophobic material, the can be processed in principle thermoplastic.

Preferred fillers which are distributed in the matrix phase are selected from the group consisting of modified and / or unmodified phyllosilicates, preferably from the class of phyllosilicates, more preferably phyllosilicates of the smectic type, in particular montmorillonites, saponites, hectorites, halloysites, beidellite, Vermiculite, Stevensite, Montronite and / or Fluorhectorite. Modified phyllosilicates are materials in which at least part of the metal cations contained in the silicates (eg Na ⁺ ) have been replaced by softer cations (for example by organic cations, such as ammonium or imidazolium cations for example in the DE 103 51 268 or the EP 0 279 313 described. Reference should be made to the disclosure content of these publications with regard to the modified phyllosilicates. Likewise, such materials are commercially available (eg. As Tixogel ^® (Sud-Chemie AG) or Bentone ^®).

Further it is preferred that the filler has a cation exchange capacity from 30 to 250 meq (milliequivalents) per 100 g.

The Addition of plasticizers in the context of the prior art easier the processing, taking strength and stiffness of the final product be reduced by the plasticizing influence. Various Types of low molecular weight to oligomeric plasticizers can be used, in particular mono-, di- and / or triesters from linear or branched aliphatic carboxylic acids with 2 to 18 carbon atoms and mono-, di- and / or trivalent ones Alcohols having 2 to 12 carbon atoms are used. Especially effectively support esters from the group of acetates, Propionates and butyrates have the thermoplasticity and processability the starch ester. Examples are, among others Esters of organic alcohols especially acetates and propionates of Glycerol in the form of its mono-, di- and triesters.

Especially triacetate (triacetin) and tripropionate (tripropionin) are preferred. The spectrum of suitable plasticizers is complemented by Milk and fatty acid esters, especially oleic esters, and vegetable oils, preferably from soya, rape and ricinus.

Preferred proportions by weight of the matrix phase, based on the molding composition, lie between 99.99 to 60 wt .-%, preferably between 99.9 and 75 wt .-%, particularly preferably between 99.9 and 80 wt .-%.

As well it is advantageous if the proportion by weight of at least one nanoscale filler based on the molding compound between 0.01 to 40 wt .-%, preferably between 0.1 and 25, more preferably between 0.1 and 20 wt .-%, in particular 2.5 to 7.5 wt .-% is.

preferred Amounts of plasticizers are between 2.5 and 40 Wt .-%, preferably between 10 and 30 wt .-%, particularly preferably between 15 and 25% by weight.

The nanoscale filler used according to the invention can vary over a wide order of magnitude with respect to its mean particle diameter d ₅₀ . Preferred ranges here are between 0.1 nm and 10 μm, preferably between 2 μm and 8 μm.

According to the invention as well as a process for the preparation of an inventive provided thermoplastic molding composition, wherein the at least a plasticizer and the at least one nanoscale filler under the influence of mechanical shear forces with the Matrix phase is mixed homogeneously and before mixing the nanoscale Filler is introduced into the plasticizer.

Prefers Here is that the mechanical shear forces a Comminution of at least part of the nanoscale filler he follows.

advantageous Processing temperatures of the manufacturing process are included between 0 ° C and 450 ° C, preferably between 75 ° C and 350 ° C, more preferably between 100 ° C and 250 ° C.

Farther becomes according to the present invention, a molded part provided, consisting of an inventive Molding material can be produced.

The Inventive molding surprisingly high mechanical strength on.

In particular, the tensile strength of the molding according to the invention is at least 25 MPa, preferably at least 27.5 MPa, more preferably at least 30 MPa, particularly preferably at least 32.5 MPa, measured on a test rod DIN EN ISO 527-1 type 5A at 23 ° C and 50% relative humidity.

Likewise, the molding according to the invention is characterized by an extremely high tensile modulus of at least 1.5 GPa, preferably at least 1.75 GPa, more preferably at least 1.9 GPa, more preferably at least 2.5 GPa, measured on a test rod DIN EN ISO 527-1 type 5A at 23 ° C and 50% relative humidity, off.

additionally According to the invention, a process for the preparation provided a molded part according to the invention, in which a molding compound is thermoplastic ver works, in particular by extrusion, injection molding and / or blow molding.

Special Uses of a molded part according to the invention are gear knobs, valve handles, keyboards, toys, Packaging, films, films for coating and / or coatings in the construction and / or furniture industry, the enumeration is merely exemplary nature.

in the Hereinafter, the present invention will be described by way of example Explanations explained in more detail, this being The invention is not limited to the specific parameters restrict.

A particular embodiment of the preparation of the material according to the invention is the following. A defined amount of the layered silicate (MMT) is introduced into the plasticizer and stored for 2 to 48 hours, preferably for about 24 hours at room temperature. Subsequently, the resulting suspension is premixed with the predetermined amount of starch ester with the aid of a rapidly rotating mixer for 1 to 10 min and so made a premix. Typical MMT contents are from 1 to 20% by mass MMT and plasticizer contents from 1 to 30% by mass, based in each case on the total mass of the mixture. Subsequently, the premix is homogenized in a kneader at temperatures in the range of 100 ° C to 250 ° C at rotor speeds between 10 and 500 rotations per minute (rpm). Preferred temperatures are in the range of 150 ° C to 210 ° C and rotational speeds between 50 rpm and 250 rpm. Mixing times are in the range between 5 min and 60 min, preferably between 10 min and 30 min. For further homogenization, an extrusion takes place on an equal Inverted twin-screw extruder at temperatures ren between 100 ° C and 250 ° C, preferably between 100 ° C and 180 ° C and a screw speed between 10 and 350 rpm, preferably between 50 and 250 rpm. The extrudate is comminuted with a commercial granulator and injection molded. Cylinder temperatures are between 100 ° C and 200 ° C, preferably between 120 ° C and 170 ° C, and mold temperatures between 40 ° C and 100 ° C, preferably between 50 ° C and 70 ° C.

In The following examples illustrate the invention Process further explained and the inventive Material characterized.

example 1

starch (SA) with a degree of substitution of 2.6 (determined by Magnetic nuclear resonance) and organo-modified silicate (MMT1) modified with dimethylbenzylhydro-tallow ammonium, are pre-dried under vacuum for 24 h at 80 ° C. 7.9 g of the layered silicate are introduced into 30 g of triacetin and 24 h stored at room temperature. Then 120 g of the dried SA added and with a rapidly rotating Blender mixed for 5 min. The resulting Premix contains 5 layered silicate and can be up to his further use sealed in a polyethylene bag be stored.

The premix is homogenized in a kneader W 350 E from the company. Brabender for 20 min at 130 ° C and a speed of 150 rpm. After discharge and comminution of the compound, it is further homogenized in a co-rotating twin-screw extruder (Haake Minilab) at 150 ° C. and 200 rpm, discharged and granulated (granulator SGS 25-E4 from Scheer). Subsequent injection molding takes place on a Haake Minijet at a cylinder temperature of 150 ° C and a mold temperature of 60 ° C. There are test rods after DIN EN ISO 527-1 type 5A subsequently produced at 23 ° C and 50% relative humidity in an air-conditioned laboratory on a Zwick 1445 testing machine DIN EN ISO 527-1 being checked. The results for strength, modulus and elongation at break are given in Table 1.

Example 2

As Example 1, only with unmodified phyllosilicate MMT2 with a CEC of 105 milliequivalents per 100g instead of the modified one Silicate. The results for strength, modulus and elongation at break are also shown in Table 1.

Comparative example

To the Comparative silicate-free SA is prepared, the method similar to Examples 1 and 2 and only omitted the steps which refer to the phyllosilicate. The results are also shown in Table 1. This creates a material which has a comparable strength with polypropylene, however has only a small elongation at break, so it is very brittle.

• * mit 20% Triacetin als Weichmacher

With 5% organo-modified phyllosilicate (Example 1), the strength can be increased by 40% and the tensile modulus is doubled. If the unmodified phyllosilicate (Ex. 2) is used, the strength and elongation are somewhat reduced, but the elongation increases tenfold and the material loses its brittleness. Table 1 material Tensile strength [MPa] Tensile modulus [GPa] Elongation at break [%] Starch acetate (SA) * (comparative example) 23.5 ± 1.5 1.3 ± 0.2 2.0 ± 0.2 SA * + 5% MMT1 (Example 1) 33.0 ± 1.4 2.7 ± 0.8 2.5 ± 0.7 SA * + 5% MMT2 (example 2) 30.0 ± 0.2 1.9 ± 0.3 23.5 ± 2.7

• * with 20% triacetin as plasticizer

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 5362777 [0004]
• WO 2005/090462 [0004]
• - US 5043196 [0004]
• US 5869647 [0005]
• - WO 2008/014573 [0006]
• WO 01/68762 [0007]
• US 2006/0107945 [0008]
• - DE 10351268 [0017]
• EP 0279313 [0017]

Cited non-patent literature

• - DIN EN ISO 527-1 type 5A [0030]
• - DIN EN ISO 527-1 type 5A [0031]
• - DIN EN ISO 527-1 Type 5A [0038]
• - DIN EN ISO 527-1 [0038]

Claims (18)

Thermoplastic molding composition comprising a matrix phase from at least one starch ester and at least one Plasticizer, wherein in the matrix phase at least one nanoscale Filler is included. Molding composition according to claim 1, characterized that the starch ester is selected from the group consisting of starch acetate, starch propionate, Starch butyrate and / or mixtures thereof. Molding composition according to one of the preceding claims, characterized in that the starch ester is a degree of substitution (DS) from 1.4 to 3, preferably from 2.1 to 2.9. Molding composition according to one of the preceding claims, characterized in that the at least one filler is selected from the group consisting of modified and / or unmodified phyllosilicates, preferably from the class the phyllosilicates, more preferably smectic phyllosilicates Type, in particular Montmorillonite, Saponite, Hectorite, Halloysite, Beidellite, Vermiculite, Stevensite, Montronite and / or Fluorhectorite. Molding composition according to one of the preceding claims, characterized in that the at least one filler a cation exchange capacity of 30 to 250 meq (milliequivalents) per 100 g. Molding composition according to one of the preceding claims, characterized in that the at least one plasticizer is selected is from the group consisting of mono-, di- and / or triesters with or without linear or branched aliphatic carboxylic acids 2 to 18 carbon atoms and mono-, di- and / or trivalent ones Alcohols having 2 to 12 carbon atoms, preferably mono-, di- and / or Triesters of glycerol, more preferably glycerol triacetate and / or Glycerintriproprionat. Molding composition according to one of the preceding claims, characterized in that the weight fraction of the matrix phase based on the molding composition between 99.99 to 60 wt .-%, preferably between 99.9 and 75 wt .-%, particularly preferably between 99.9 and 80 wt .-% is. Molding composition according to one of the preceding claims, characterized in that the weight proportion of the at least one nanoscale filler based on the molding compound between 0.01 to 40 wt .-%, preferably between 0.1 and 25, particularly preferably between 0.1 and 20 wt .-%, in particular 2.5 to 7.5 wt .-% is. Molding composition according to one of the preceding claims, characterized in that the weight proportion of the at least one Plasticizer based on the molding composition between 2.5 and 40 wt .-%, preferably between 10 and 30% by weight, more preferably between 15 and 25 wt .-% is. Molding composition according to one of the preceding claims, characterized in that the at least one nanoscale filler has a mean particle size d ₅₀ between 0.1 nm and 10 microns, preferably between 2 microns and 8 microns. Process for producing a thermoplastic Molding composition according to one of the preceding claims, wherein the at least one plasticizer and the at least one nanoscale Filler under the action of mechanical shear forces is homogeneously mixed with the matrix phase, characterized that before mixing the nanoscale filler in the Plasticizer is introduced. Method according to the preceding claim, characterized characterized in that by the mechanical shear forces a comminution of at least part of the nanoscale filler he follows. Method according to one of the two preceding claims, characterized in that the mixing at temperatures between 0 ° C and 450 ° C, preferably between 75 ° C and 350 ° C, more preferably between 100 ° C and 250 ° C is performed. Molded part, producible from a molding compound after a of claims 1 to 10. Molding according to the preceding claim, characterized by a tensile strength of at least 25 MPa, preferably at least 27.5 MPa, more preferably at least 30 MPa, more preferably at least 32.5 MPa, measured on a test rod according to DIN EN ISO 527-1 type 5A at 23 ° C and 50% relative air wet. Molding according to one of the two preceding claims, characterized by a tensile modulus of at least 1.5 GPa, preferably at least 1.75 GPa, more preferably at least 1.9 GPa, especially preferably at least 2.5 GPa, measured on a test rod according to DIN EN ISO 527-1 type 5A at 23 ° C and 50% relative Humidity. Process for producing a molded article according to one of claims 14 to 16 wherein a molding compound after a of claims 1 to 10 is processed thermoplastically, in particular by extrusion, injection molding and / or blow molding. Use of a molding according to one of the claims 14 to 16 for control knobs, mixer handles, keyboards, Toys, packaging, films, films for coating and / or coatings in the construction and / or furniture industry.