DE19849186A1 - Additives to improve the barrier properties of polymers - Google Patents

Abstract

The invention relates to additives for polymers and copolymers which bring about an improvement in the barrier properties against gases, aromas and water vapor and also an improvement in the processing properties. DOLLAR A The additives according to the invention are polymers containing carbonic acid ester and / or carboxylic acid ester groups, which are obtained by copolymerization of carbon dioxide and epoxides and also modified with lactones and in the production of granules of the polymers in proportions of 0.1 to 15% by weight, based on the Base polymers, as well as barrier layers or as a coating.

Description

The invention relates to additives for polymers or copolymers, the barrier egg improve properties against gases, water vapor and aromas as well Simultaneously simplify processing and mechanical properties properties of the polymers do not change or change positively.

The demands for high-quality packaging films that come from profitability found thinner, with a high barrier effect, environmentally friendly and possible As recyclable as possible, have increased significantly recently.

It is known that the production of films with a high barrier action against Ga se and water vapor in most cases require a lot of effort and are also very expensive.

Today ethylene-vinyl alcohol copolymers are predominantly used as barrier plastics (EVQH) and polyvinylidene chloride (PVDC) are used. Barrier plastics can all systems used for film production can be used. The most common The processes used are coextrusion, coating / painting and Metallization.

They are mainly used as composite materials for the construction of barrier films Polyethylene, polypropylene, polyethylene terephthalate, polyamide and polycarbonate set.

In most cases, adhesion promoters still have to be used for the strength of the composites and to meet all requirements and external influences often a complicated composite structure is necessary.

Most barrier films are used for food packaging. For example, EP 0645417 describes a biaxially oriented polypropylene film with ver described better water vapor barrier. To the appropriate water vapor To reach the barrier, the polymer matrix is made of natural or synthetic resins added, the film must have a certain chain isotaxy index.  

In the preferred form, the films have outer layers or are multi-layered built up.

EP 0441027 describes a ternary mixture of isotactic polypropylene, HDPE and a low molecular resin for the production of films with improved Barrier properties suggested. The ternary mixture is extruded together dated and then stretched. The resin content is described in the Mixtures generally very high (»5%).

In WO 97/11116 an attempt is made to influence the crystallinity of Propylene homopolymers and copolymers to improve water vapor permeability. There are lower water vapor permeability than with HD polyethylene hold.

In EP 0341188 the barrier properties of polyolefins are determined by the additives administration of up to 10% of a partially incompatible wax. By Annealing should further improve the barrier effect nen.

In WO 97/12927 a thermoplastic copolyester is described, the verbes should have gas barrier properties. Furthermore, the manufacturing should only little or no acetaldehyde is produced.

The copolyester contains 10 to 100 mol% naphthalenedicarboxylic acid, 90 to 0 mol% Terephthalic acid and as alcohol component 100 mol% 1,4-cyclohexanedimethanol, the 1,4 cyclohexanedimethanol having a cis isomer content of at least 50% Has. The barrier properties against oxygen and carbon dioxide should be the same or be better than that of polyethylene terephthalate.

All these possibilities and technologies described to improve the bar rier properties of plastics, representative of a large number of Variants stand, in addition to the advantages described, also have disadvantages.

In order to achieve acceptable barrier properties, it often has to be very complex Technologies for the production of complex multilayer films or  expensive barrier materials are used. This effort is necessary unnecessarily high costs.

Furthermore, additives are also used. To get good results Chen, these must be used in high concentration, which can be disruptive Block tendencies in further processing and also to resin deposits in the Processing machines leads.

The results achieved by the mostly cost-intensive procedures ge often do not meet the required level or are disproportionate to the level wall and benefits.

The object of the invention is therefore to provide an inexpensive and simple solution find a Ver. with little effort and material for different polymers to achieve better barrier properties. At the same time, the mechani properties of the polymers and the processing parameters are not or can only be changed in a positive way.

The additives to be used according to the invention are, analogously to DE 197 50 288, carbonic acid ester and / or carboxylic ester groups containing polymers of the general formula

where R ₁ , R ₂ , R ₃ , R ₄ , R _{5 are} hydrogen or alkyl. The following also applies:
0 ≦ x Y, z <∞, where at least one value must be <0 and 1 <n <10 ⁴ .

These polymeric additives can, for example, be very easily by anionic Po Lymerization of carbon dioxide with one or more epoxides as aliphatic Polycarbonates or by anionic polymerization of carbon dioxide, epoxides and lactones are produced as modified aliphatic polycarbonates.

Also block copolymers are made of carbon dioxide with two different epoxies usable according to the invention.  

These additives are advantageously added to the polymers in the granulation process mixed in. It is also possible to use this additive, depending on the intended use during the manufacturing process for any semi-finished products (blown films, thermoforming fo lien, preforms, etc.). Similarly, the additives can also be used as a batch be dosed.

The polyalkylene carbonates are added to the polymers in proportions of 0.1 to 15% by weight, based on the polymer added. 0.1 to 10% by weight are particularly advantageous, preferably 0.5 to 5% by weight.

Particularly good results are obtained with polyesters, e.g. B. polyethylene terephthalate, aromatic polycarbonates, polypropylene, polyethylene obtained. But also with other polymers such as B. polystyrene, polyvinyl chloride and. a. can use it become.

A particular advantage is that when using these additives largely on Ver bundle films or coated films can be dispensed with. The barrier achieved properties already meet demanding requirements in single-layer films. The barrier effect is further increased by subsequent biaxial stretching.

In addition to improving the barrier against gases, water vapor and aromas processing temperature when using this additive for some polymers ratures are significantly reduced. This applies in particular to polymers that need a high processing temperature, such as B. aromatic polycarbonates or polyethylene terephthalate.

The special advantage of this additive lies in its combination effect. One On the one hand, this affects the improvement of the barrier against gases, water vapor and Flavors and on the other hand the effect as processing aid and as modifier goal.

Deposits on machine parts were not observed.

Using some examples, the mode of action of aliphatic polycarbo nate on the properties of the polymers.

example 1

5.3 kg of methylene chloride and 1.7 kg of propy were added to a 10 l stirred reactor lenoxid and 40 g zinc carboxylate (mixture of zinc salts of the dicarboxylic acids of the C numbers 5 and 6) mixed and saturated with carbon dioxide at 20 bar. Then ßend was heated to 75 ° C and stirred for 5 hours at this temperature. After cooling, the reactor was depressurized, the polymer solution with dilute Washed sulfuric acid. The polymer was precipitated and finely divided with methanol dried at room temperature. The polypropylene carbonate thus obtained was granulated and used in this form as an additive. The granules were in one Amount of 3 wt .-% a polypropylene added during the granulation process puts. This polypropylene granulate had a melt index of 8.2 g / 10 min (230 ° C; 2.16 kg). A flat film of thickness was made from this polypropylene granulate of approx. 100 µm and the permeability of water vapor and oxygen measured.

For comparison, a flat film made of polypropylene without an additive was produced under the same conditions and measured for permeability. From the measurement results it can be seen that by adding the polypropylene carbonate z. B. the water vapor permeability is reduced by approximately 50% from 0.87 g / m ² d to 0.42 g / m ² d. The oxygen permeability is reduced by about 30% from 401 to 274 cm ³ / m ² d bar.

With largely unchanged mechanical properties, the addition of polypropylene carbonate the modulus of elasticity increased by 25%.

Example 2

1.3 kg of methylene chloride, 0.265 kg of ethylene oxide and 10 g of zinc carboxylate were placed in a 2 l pressure reactor. This mixture was saturated with carbon dioxide with stirring at room temperature, then brought to 65 ° C. and kept at this temperature for 5 hours. After cooling and relaxing, the poly mers were precipitated with methanol and dried in a vacuum oven at ambient temperature. The polyethylene carbonate thus obtained was mixed in an amount of 3% by weight, based on the base polymer polypropylene, of the polymer melt during the manufacturing process for a flat film. The melt index of the polypropylene was 6 g / 10 min (230 ° C; 2.16 kg). The measurement of the oxygen permeability showed a reduction in the oxygen permeability by approx. 15% from 405 to 330 cm ³ / m ² d bar compared to a sample without additive, while the water vapor barrier by 25% from 0.89 to 0.63 g / m ² d was improved. The mechanical values remained unchanged.

Experiments showed that the barrier effect can also be improved by biaxial stretching. For example, water vapor permeability of a PP flat film without additive was reduced by stretching from 1.2 g / m ² d to 0.7 g / m ² d. However, the leap in quality is significantly increased if the additive has been added to the base material during film production. The water vapor permeability could be reduced to 0.40 g / m ² d here.

Example 3

5.5 kg of methylene chloride, 450 g of ethylene oxide and 420 g were placed in a 10 l pressure reactor Propylene oxide and 45 g of zinc carboxylate submitted. This mixture is stirred saturated with carbon dioxide at room temperature. The carbon dioxide pressure was 12 bar. After completion of the saturation phase, the reaction mixture was opened 70 ° C heated and polymerized with stirring at this temperature for 5 hours. After cooling and relaxing, the terpoly dissolved in methylene chloride Precipitated mers with methanol and in a vacuum drying cabinet at room temperature dried.

The terpolymer obtained in this way was granulated and in this form as an additive in an amount of 2.5 wt .-% in polyethylene terephthalate in the manufacture of Preforms for beverage bottles added. With the process thus made possible A temperature reduction of 25 K prevented the formation of acetaldehyde be knitted.  

The barrier to oxygen improved in the permeation coefficient by approximately a power of ten from 3.8 E-03 to 4.1 E-04 cm ³ / m ² d atm.

Example 4

2.75 kg of methylene chloride, 0.85 kg of propylene oxide and 20 g of zinc carboxylate were placed in a 5 l pressure reactor. This mixture was saturated with carbon dioxide at room temperature with stirring and under a pressure of 15 bar. This mixture was polymerized at a temperature of 75 ° C. for 5 hours. The polymer was worked up as in Examples 1 to 3 and used as an additive in the manufacture of flat films made from aromatic polycarbonate. The amount used was 3 to 5% by weight. Even when using 3% polypropylene carbonate (PPC), the process temperature could be reduced by approx. 25 K. PPC in no way impaired the high transparency of the polycarbonate. The improvement of the barrier against oxygen was up to 70% z. B. from 460 to 124 cm ³ / m ² d atm.

Example 5

In a 10 l pressure reactor flushed with nitrogen and carbon dioxide, 830 g Propylene oxide, 250 g β-butyrolactone and 45 g zinc carboxylate in 5.3 kg methylene chloride rid submitted. This reaction mixture was then added with carbon dioxide 22 ° C saturated and then heated to 85 ° C. The polymerization time be wore 6.5 hours. After cooling and releasing the reaction solution with diluted sulfuric acid and water thoroughly washed and fine with methanol partially precipitated, filtered and at room temperature under vacuum to the weight con punch dried.

This modified polypropylene carbonate thus produced was added in an amount of 3.5% in the production of polyethylene granules. The blown film produced from this had a reduced oxygen permeability compared to that without an additive. The value was improved from 2000 cm ³ / m ² d bar to 1050 cm ³ / m ² d bar.

Example 6

For the production of a polyalkylene carbonate, which is formed as a block copolymer is, 2.5 kg of methylene chloride, 410 g of propylene oxide and. were in a 5 l pressure reactor 30 g of zinc salt, as used in Examples 1 to 5, presented and this Mi saturated with carbon dioxide at 23 ° C and 20 bar and then 3 hours polymerized at 80 ° C. The reaction mixture was then reduced to 20 ° C cooled and with a pressure pump 400 g of ethylene oxide in the reactor filled. The temperature of the reaction mixture was then brought to 65 ° C and the carbon dioxide pressure is kept at 37 bar via a control valve. After another 3 The resulting polymer solution was cooled, relaxed and filtered for hours. The Polymer was precipitated with methanol, separated and 24 at room temperature Hours dried.

The block copolymer thus produced was made as a barrier layer in composite films Polypropylene used. The oxygen barrier has been improved by a factor of 3. The use of adhesion promoters could be dispensed with.

Claims (7)

1. Additives to improve the barrier properties of polymers and copolymers according to DE 1 97 50 288, characterized in that they contain carbonic acid ester and / or carboxylic ester groups containing polymers of the general formula
are, where R ₁ , R ₂ , R ₃ , R ₄ , R _{5 are} hydrogen or alkyl and 0 ≦ x, y, z <∞, where at least one value must be <0 and 1 <n <104 and that they are used in proportions of 0.1 to 15% by weight, based on the polymer. 2. Additives according to claim 1, characterized in that they are aliphatic polycar bonates are those that are obtained by copolymerizing carbon dioxide with one or more Ren epoxides are produced. 3. Additives according to claims 1 and 2, characterized in that they with Lactones are modified aliphatic polycarbonates. 4. Additives according to claims 1 to 3, characterized in that they are as Block polymers are formed. 5. Additives according to claims 1 to 4, characterized in that they are in An parts of 0.1 to 10 wt .-%, in particular 0.5 to 5 wt .-%, are used.   6. Additives according to claims 1 to 5, characterized in that they are as Barrier layer or as a coating to improve the barrier of poly mers and copolymers against gases, flavors and water vapor become. 7. Additives according to claims 1 to 6, characterized in that they are in poly esters, polycarbonates, polyolefins and vinyl polymers can be used.