DE19511579C1 - Thermoplastic moulding material from synthetic and natural polymers - Google Patents

Abstract

The prodn. of thermoplastic moulding materials from synthetic polymers (I) and natural polymers (II) comprises melting 36-75 wt.% (I) in an extruder, adding 0.3-3.0 wt.% functional monomer (III) and 0.1-1.0 wt.% radical initiator, reacting the mixt. at increasing temps. in the range 150-270 deg. C, cooling to below 200 deg. C, and incorporating 21-60 wt.% (II) to give a homogeneous mixt.

Description

The invention relates to a method for producing thermoplastic processable molding compounds consisting of synthetic and natural polymers used in the manufacture of Moldings suitable by extrusion, pressing and injection molding are.

The finishing of synthetic polymers with additives is a proven process for modifying the product's own create. As is well known, the usage properties improve plastics by adding fillers. The Production of molding compounds from thermoplastic and filler but also follows in order to save polymer material or to open up new areas of application.

Both inorganic and organic fillers are used Materials used, e.g. B. talc, asbestos, glass fibers. Of course Liche polymers show due to their hydrophilic properties only low compatibility with the mostly hydrophobic syn synthetic polymers. So mere mixing or Do not knead the two components in conjunction with freeze properties. To improve tolerance between natural polymers and the synthetic polymer Numerous works were carried out.

According to one way of working, the surface of the filler exposed to treatment that begins tolerability increases, e.g. B. Coating the filler.  

Kneading surface-active substances in is also known the polymer matrix.

Another way of working is trying by using poly mers with polar groups as a polymer backbone a certain Achieve tolerance. This is how carbonyl groups can be modified polymers by grafting with unsaturated car produce bonic acids, esters or anhydrides, which are known as Compatibilizers are suitable. Such implementations can be found in Extruders or thermoplastic kneaders can be carried out.

According to EP 540 026 compositions from 10 to 70% cellu loose material and polyolefins with the addition of MSA-ge grafted polypropylene as a compatibilizer. Of the Scope of this procedure is easy flowing polyolefin types with MFI <20 dg / min (230 ° C) borders.

According to EP 57 967, vegetable fibers are combined with polyolefins trimmed. The tolerance is made with acid modifier polyolefins.

Both technical solutions require the deployment of the Graft copolymers used as compatibilizers in one separate process stage. Mixtures have insufficient Homogeneity. To ensure a homogeneous distribution in the poly Long mixing times are required to achieve mermatrix.

According to US 3 645 939 is a hydropho with MSA and peroxide the hydroxyl group-containing material is carried out, the mixture is then mixed with the thermoplastic. The Pretreatment of the natural polymer is not very effective  and provides the necessary procedural step of the Mixing and homogenizing represent an additional step. Inadequate mechanical properties are achieved.

According to EP 8143, 30 to 70% cellulose fibers and 70 to 30% modified polyolefin or polyolefin with MFI <0.5 homogenized up to 10 dg / min and polar monomer by mixing.

DE 1 902 828 describes a one-step process in which the Linking both components by MSA / peroxide mixture should be enough. But since the cellulose-containing materials are not thermally resilient, the implementation at Tempe temperatures <200 ° C.

The invention specified in claim 1 was the object basic molding compounds made of natural and synthetic poly meren without much effort in procedurally simple To produce ways that ver due to a homogeneous structure better usage properties and a corresponding ther Show Mooxidative resistance and extru for production dated, pressed or injection molded parts or semi-finished products are suitable.

The task was principally solved by the fact that the syn synthetic polymers in an extruder with increasing temperature temperature profile in the presence of radical initiators functional monomers grafted and then at falling temperature profile into the natural polymer Melt is incorporated homogeneously.  

In this way, the processing properties of the Molding compounds not affected. The separated temperature guidance for grafting and compounding enables a advantageous control of the individual processes. The technology enables low-cost production of the compounds. They are not processing stabilizers and plasticizers training aids necessary.

The inventive method has the advantage that described incorporation of the natural polymers in the Melt the mixing process is relatively short, so that thermal damage is largely prevented. In addition, the energy requirement for this one-stage Process less, the repeated melting is not necessary. Production is becoming tighter and faster.

The synthetic polymers are advantageous in the proportion range from 46 to 55% by mass and the natural polymers used in the range of 41 to 50 mass%.

They are preferably used as the synthetic polymer matrix known olefin polymers are used. The poly Merisates are characterized by an MFI between 0.5 and 200 dg / min, preferably 0.5 to 15 dg / min, and a density between 0.89 and 0.99 g / cm³. Olefin polymers are here in the homopolymers of ethylene and propylene, their Copolymers and their mixtures, styrene polymers and copolymers. The polymer component can also be regrind and / or waste such as B. from the polyolefin light fraction the collection system. The use of mixed art fabrics has proven to be particularly cheap because the improved flow properties lower processing enable temperatures.  

The natural polymers are cellulose and / or lignocellu loose material, e.g. B. ground wood, straw, paper (waste) and shell flour or mixtures thereof. These Fabrics are very inexpensive. For the invention Process the material in the form of fine chips, Short fibers and powder used. There are materials in the Particle size range from 10 to 7000 microns in length and 10 to 2000 µm thick. The moisture content is below 6%.

Compounds which are suitable as functional monomers are have high affinity for natural polymers: acrylic acid, Acrylic ester, N-methyl acrylamide, glycidyl methacrylate, Maleic anhydride, phthalic anhydride, vinyl chloride, Ethylene-vinyl acetate copolymers and. Ä.

As radical-forming substances (initiators) are preferred wise peroxides such as dibenzoyl peroxide, dicumyl peroxide, ditert. butyl peroxide, tert-butyl perbenzoate and methyl ethyl ketone per oxide suitable.

In addition to the main components, the molding compositions can also be conventional Additives such as stabilizers, lubricants, dyes, pigments, Flame retardants and / or blowing agents in usual amounts contain. The production of the molding compositions according to the invention takes place on extruders.

For the process, twin screw extruders with kneading, Return, mixing and dispersing elements are suitable. she allow setting for modification, compoundie necessary parameters.  

The housing of the extruder used was with several on running openings equipped for the addition of the components. Another opening was used to degas the melt a vacuum system. The screw conveyor was in different Zones divided, the temperature in these zones in was individually and independently adjustable. Of the Extruder was pressure-tight, so that reactions under Could be carried out under pressure or under vacuum. The Kneaders were continuously working metering devices upstream.

The synthetic polymer component, the functional monomer and the peroxide were in the first inlet of the extru drove it. Liquid components were kneaded over drilled dosed into the process part.

The synthetic polymer component came through Einzugsele elements in the melting and homogeneity zone. At the end of this Process part lay a modified melt with the ge desired viscosity temperature level.

The natural polymer was in the second inlet driven over a conveyor. The corresponding ver part consisted of a mixing and dispersing zone. At the The polymers were at the end of this part of the process mixes and disperses. The compound or the molding compound was in the last zone of the extruder degassed extensively via a vertical degassing dome, in a Water bath extruded and granulated. Form made in this way masses are with common processing methods such as spray casting, extruding, pressing, calendering into shaped bodies and semi-finished products can be processed.  

Direct extrusion enables molded parts such as profiles manufacture, through injection molding processing are technical Components are obtained, panels can be pressed testify.

Embodiments

The following were used as synthetic polymers:

- film regranulate
Density: 0.921 g / cm³
MFI: 0.75 dg / min (190 ° C; 21.2 N)

- polypropylene recyclate
Density: 0.91 g / cm³
MFI: 5 dg / min (230 ° C; 21.2 N)

- HDPE bottle regrind
Density: 0.954 g / cm³
MFI: 0.54 dg / min, 0.37 dg / min (190 ° C; 21.2 N)

The following were used as natural polymers:

- wood flour (fir)
Moisture content: 3.5%
Particle size: 250-500 µm
Bulk density: 0.2-0.3 g / cm³

- Straw
Moisture content: 5.6%
Particle size: 10-2000 µm
Bulk density: 0.1-0.15 g / cm³

The tensile stress-strain behavior was measured on the test specimens (DIN 53 455), the bending deformation behavior (ASTM-D 790-80), the impact strength (DIN 53 453), the moisture (DIN 51 777) and the thermooxidative stability (DIN 53 384, Part 1) was examined.

example 1

A synchronous 2-screw kneader of the type ZSK, which was equipped in the manner described, 29 kg / h of poly propylene recyclate, 0.9 kg / h of maleic anhydride and 0.1 kg / h of dicumyl peroxide were fed to the feed zone heated to 170 ° C. leads. The screw speed was 200 min ^-1 . The mixture was reacted under the influence of a temperature profile rising to 270 ° C. After the melt had cooled to 190 ° C., 30 kg / h of wood flour were mixed in continuously. A vacuum of 120 mbar was applied to the degassing device and water and fission products were drawn off. The molding compound was discharged at a temperature of 200 ° C. The material characteristics are given in Table 1.

Example 2

The procedure was as in Example 1. 33 kg / h of HDPE regrind, 1.3 kg / h of maleic anhydride and 0.15 kg / h of dibenzoyl peroxide were metered into the extruder via the feed nozzle. The feed zone was set to a temperature of 165 ° C. In the subsequent zones, the temperature was raised to 235 ° C. The extruder was operated at a speed of 160 min ^-1 . After the melt had been heated to 170 ° C., 15 kg / h of straw were added and homogeneously worked in. The mixture was degassed at a pressure of 100 mbar. The molding composition thus produced was discharged at a temperature of 185 ° C. and then granulated. It had the properties determined in Table 1.

Example 3

The following experiment was carried out on the extruder used in Examples 1 and 2:
40 kg / h recycled polypropylene were mixed with 0.2 kg / h dicumyl peroxide and placed in the first inlet opening of the extruder. 1.8 kg / h of acrylic acid were metered in via a metering nozzle. The extruder was operated at a speed of 220 min ^-1 . The temperature, which was 175 ° C. in the feed zone, was increased to 265 ° C. in the following zones. After the modified melt was cooled to 170 ° C., 28 kg / h of ground straw were kneaded in. After passing through the homogeneity zone, the mixture was degassed from volatile constituents at a negative pressure of 130 mbar. The characteristic values listed in Table 1 were determined on the product discharged at 185 ° C.

Example 4

Example 3 was repeated with the following changes. A mixture of 42 kg / h LDPE film regranulate and 0.15 kg / h diamyl peroxide were fed to the extruder via the first feed pipe. 1.2 kg / h of acrylic acid were continuously added via the metering nozzle. The temperature in the feed zone was 150 ° C. The screw speed was 180 min ^-1 . The maximum temperature reached 230 ° C.

The melt was then cooled to 160 ° C. 18 kg / h wood flour incorporated homogeneously. The degassing of the finished molding compound was carried out at a pressure of 120 mbar.

The determination of characteristic values on test specimens resulted in Table 1 compiled values.

Example 5

A mixture of 38.8 kg / h polypropylene / HDPE recyclate was fed according to the technology of Example 3 together with 0.24 kg / h dicumyl peroxide to the extruder via the first inlet nozzle. 0.24 kg / h of acrylic acid were continuously added via the intermediate connector. The screw speed was 150 min ^-1 . The maximum temperature reached 245 ° C. Finally, 20 kg / h of wood flour were homogeneously incorporated into the melt, which had cooled to 160 ° C. The finished molding compound was degassed at a pressure of 110 mbar.

The determination of characteristic values on test specimens resulted in Table 1 compiled values.  

Table 1

Test results of the molding compounds produced

Claims (11)

1. A process for the preparation of thermoplastic molding compositions from synthetic and natural polymers in the presence of functional monomers and radical-forming substances, characterized in that 36 to 75% by mass of the synthetic polymer is melted in an extruder, 0.3 to 3.0% by mass functional Monomer and 0.1 to 1.0 mass% radical generator are added, the mixture is reacted with increasing temperature profile in the range from 150 to 270 ° C, after tempering to <200 ° C 21 to 60 mass% of the natural polymer homogeneously mixed who the and the mixture is discharged. 2. The method according to claim 1, characterized in that 46 to 55 mass% of the synthetic and 41 to 50 mass% of the natural polymer can be used. 3. The method according to claim 1 or 2, characterized in that mate containing hydroxyl groups as natural polymers rialien, preferably wood, straw, paper and / or scha len flour, can be used. 4. The method according to claim 1 to 3, characterized in that the natural polymers in the form of short fibers or Powders in the particle size range from 10 to 7000 µm in length be incorporated. 5. The method according to claim 1 to 4, characterized in that the moisture content of natural polymers <6%, preferably <3.5%.   6. The method according to claim 1 to 5, characterized in that as synthetic polymers thermoplastic hydrocarbon based, preferably Polyethylene and polypropylene, their copolymers and their Mixtures, polystyrene and styrene copolymers. 7. The method according to claim 1 to 6, characterized in that that as synthetic polymers in addition to new goods also rain rate and / or used plastics. 8. The method according to claim 1 to 7, characterized in that that as functional monomers unsaturated compounds with functional groups, preferably acrylic acid, acrylic ester, N-methyl acrylamide, glycidyl methacrylate, male acid anhydride, phthalic anhydride, vinyl chloride and Ethylene-vinyl acetate copolymers are used. 9. The method according to claim 1 to 8, characterized in that as radical-forming substances organic peroxides, preferably dibenzoyl peroxides, dicumyl peroxide, di-tert. butyl peroxide, tert-butyl perbenzoate and methyl ethyl ketone peroxide. 10. The method according to claim 1 to 9, characterized in that that the mixtures in addition to synthetic and natural Polymers other additives typical of plastics in the form of Stabilizers, lubricants, dyes, pigments, Flame retardants and / or blowing agents are added. 11. Use of the molding compositions according to claim 1 to 10 for Her provision of molded articles by extrusion and injection pour as well as transfer presses.