NL8102012A - POLYALKENE PLASTIC COMPOSITION WITH IMPROVED TRANSPARENCY PROPERTIES. - Google Patents

Description

#. . ί '1 Ν.0. 30103

Polyolefin plastic composition with improved transparency properties_

The present invention relates to a polyolefin plastic composition with improved transparency properties.

Polyolefins, for example polyethylene or polypropylene, have found many applications as packaging materials and containers in the form of films, sheets or hollow articles, but their use is limited due to their poor transparency. In particular, they are unsuitable as packaging materials or containers for articles to be visible through them (eg cosmetics or foodstuffs).

Attempts have been made to improve the transparency of olefins by including certain types of additives. For example, para-tert-butyl benzoic acid, its salts, low molecular weight waxy polyethylene and low molecular weight waxy polypropylene have been proposed as such additives. However, these customary additives are unsuitable for effecting a sufficient improvement in transparency because they reduce the mechanical and chemical properties of the products or have poor miscibility with the polyolefins.

Recently, as described in U.S. Pat. No. 4,016,118, a polyolefin plastic composition has been proposed with improved transparency and reduced strain shrinkage properties containing the compound dibenzylidene sorbitol.

While this additive has proven to be better than the previously proposed for improving the transparency properties of polyolefin plastic compositions, it would be desirable to further improve the transparency of such polyolefins without adversely affecting the mechanical and chemical properties of polyolefins. the finished products. *; to influence. Accordingly, the present invention provides an additive which can improve the transparency of polyolefins even when compared to the previously known product dibenzylidene sorbitol, which cannot reduce the mechanical and chemical properties of the final products.

According to the present invention there is provided a polyolefin-plastic composition with improved transparency comprising a polymer selected from aliphatic polyolefins and copolymers containing at least one aliphatic olefin and one or more ethylenic saturated comonomers and which contains at least one di-acetal of sorbitol, which di-acetal as sorbitol has the structure of the formula-sheet wherein R 1, R 2, R 2 and R 2 are selected from hydrogen, alkyl with a small number of carbon atoms hydroxy, methoxy, mono and di-alkylamino, amino, nitro and halogen, with the proviso that at least one of the groups - R 1, R 2, R 1 and R 1 is chlorine or bromine.

Regarding the given structural formula, it is noted that while only the 1.3: 2.4 isomer is proposed, this structure is given for convenience only and the invention is not limited to only isomers of the 1.3: 2.4 type, but may also include any other isomers as long as the compound contains two aldehyde substituents on the sorbitol moiety.

The diacetal of the present invention may be a condensation product of sorbitol and benzaldehyde or a substituted benzaldehyde. At least one of the benzaldehyde or substituted benzaldehyde moieties is substituted in one or both of the meta and para positions with a halogen atom such as chlorine and bromine. Substituents which can be used in the substituted benzaldehyde moiety at any of the ortho, meta and para sites include, for example, in addition to chlorine and bromine, which must be present in either or both meta and para sites at at least one of the aldehyde substituents, alkyl with a small number of carbon atoms, for example with 1 to about 5 carbon atoms, hydroxy, methoxy, mono- and di-alkylamino, amino and halogen other than chlorine and bromine. Preferred diacetals of the present invention include di-p-chlorobenzylidene sorbitol, di-m-chlorobenzylidene sorbitol, O-benzyliden-Op-chlorobenzylidene sorbitol, di-m-bromobenzylidene sorbitol and bis- (3,4 -dichlorobenzylidene) sorbitol.

The diacetals of the present invention can be conveniently prepared by various techniques, some of which are known. Generally, such methods employ the reaction of 1 mole of D-sorbitol with about 2 moles of aldehyde in the presence of an acidic catalyst. The temperature used in this reaction will vary widely depending on the properties, such as melting point, of the aldehyde used or the aldehydes used as the starting material in the reaction. The reaction medium can be an aqueous medium or a non-aqueous medium. A very effective process which can be used for the preparation of the diacetals of the invention is described in U.S. Pat. No. 3,721,682. While this patent is limited to benzylidene sorbitols, it has been found that the diacetals of the present invention can also be efficiently prepared according to the process described therein.

The sorbitol diacetals of the present invention prepared by the aforementioned techniques may contain a minor or even a major amount of monoacetal and triacetal by-product as impurities. Although it is not always necessary to remove these impurities prior to the incorporation of the deacetal into the polyolefin, it may be desirable to carry it out and such purification may serve to increase the transparency of the resin produced thereby. Purification of the diacetal can, for example, be carried out by removing tiacetal impurities by extracting them with a relatively non-polar solvent. By removing impurities, the product can be purified so that the amount of deacetal in the additive composition contains at least about 90% and even up to 95% deacetal or more.

As illustrated in the figure with respect to the specific compound di-p-chlorobenzylidene sorbitol, the amount of diacetal in the composition of the present invention is an amount sufficient to improve the transparency of the composition. Generally, from about 0.01 to about 2 wt.%, Preferably from about 0.1 to about 1 wt.%, Based on the total weight of the composition, can be provided. When the diacetal content is less than about 0.01 wt.%, The resultant preparation may not be sufficiently improved with respect to the transparency properties. When the diacetal content is greater than about 2% by weight, no additional benefit can be observed.

The polyolefin polymers of the present invention may include aliphatic polyolefins and copolymers containing at least one aliphatic olefin and one or more ethylenically unsaturated comonomers. Generally, the comonomer, if present, will be provided in a minor amount, for example about 10% or less or even about 5% or less, 8102012% by weight of the polyolefin. Such comonomers can serve to promote the improvement of the transparency of the polyolefin, or they can function to improve other properties of the polymer. Examples include acrylic acid, vinyl acetate, etc. Examples of olefin polymers, the transparency of which can be effectively improved according to the present invention, are polymers and copolymers of aliphatic mono olefins containing from 2 to about 6 carbon atoms which have an average molecular weight of about 10,000 to about 500,000, preferably about 30,000 to about 300,000, such as polyethylene, polypropylene, crystalline ethylene-propylene copolymer, poly (1-butene), and polymethylpentene.

The polyolefins of the present invention can be described as substantially linear, regular polymers, which may optionally contain side chains such as are found, for example, in conventional low density polyethylene.

The olefin polymer or copolymer used in the composition of the present invention is crystalline and the light diffraction caused by microcrystals contained therein is considered responsible for the deterioration of the polymer transparency. The di-acetal in the composition is believed to function to decrease the size of the microcrystals, improving the transparency of the polymer.

The composition of the present invention can be obtained by adding a specific amount of the deacetal directly to the olefin polymer or copolymer and mixing only this with any suitable agent. Also, a concentrate containing about 10% by weight of the deacetal in a polyolefin main mass 30 can be prepared and then mixed with the resin.

Other additives such as a transparent colorant or plasticizers (eg dioctyl phthalate, dibutyl phthalate, dioctyl sebacate or dioctyl adipate) can be added to the composition of the present invention as long as they do not adversely affect the improvement of the transparency of the product. It has been found that plasticizers, as mentioned above as an example, do in fact contribute to the improvement of transparency by the deacetal.

With respect to other additives, it may also be desirable to use the aforementioned di-acetals in combination with other conventional additives having known transparency enhancing effects, such as, for example, para-tert-butyl-fa Etc acid, salts thereof, low molecular weight wax polypropylene and the like. It may even be desirable to provide the special diacetals of the present invention in the polyolefin composition in combination with the dibenzylidene sorbitol additives described in U.S. Patent No. 1,016,118. In such applications, generally at least about 10, preferably about 25%, and even about 10% or more of the transparency enhancing component will be the diacetals of the present invention, the remainder being other known transparency enhancing agents. means »we ekmakers» etc ..

The composition of the present invention is suitable as a packaging and container material for cosmetics and foodstuffs because it provides films, sheets or hollow articles with improved transparency properties and better mechanical and chemical properties.

Example I

20 Preparation of di-p-chlorobenzylidene sorbitol (I)

In a 1 liter round bottom flask equipped with a stirrer, nitrogen gas inlet tube, Dean-Stark trap and cooler, 65.0 g (0.25 mol) were added 70 wt.% Water containing sorbitol, 70.3 g. 50 mol) p-chlorobenzaldehyde, 15 ml of dimethyl sulfoxide, 2.0 ml of 70 w / w methanesulfonic acid and 500 ml of cyclohexane. The mixture was stirred vigorously under a nitrogen atmosphere and heated to reflux. When the theoretical amount of water was distilled from the mixture, the reaction was stopped. During the refluxing period, a thick, white precipitate of the product was formed. The precipitate was neutralized with triethylamine, filtered, washed thoroughly with water and dried, yielding 66.2 g of product as a white powder.

The product was purified by slurrying in 10 w / v% dioxane and the resulting mixture was stirred at 50 ° C for 1 hour. The mixture was filtered and the resulting solid was washed with additional dioxane and dried. The product had a melting point of 244-247 ° C and was approximately 95% pure by high pressure liquid chromatography.

81 0 2 0 1 2 * 6 «

Example II

Preparation of O-Benzylidene-On-Chlorobenzylidene-Sorbitol (II) O-Benzylidene-On-chlorobenzylidene-Sorbitol (II) was prepared according to the procedure of Example I using equimol-5 amounts of benzaldehyde and p-chlorobenzaldehyde. Duk was isolated as a mixture with dibenzylidene sorbitol (DBS) and di-p-chlorobenzylidene sorbitol (DCBS) as evidenced by high pressure liquid chromatography. The approximate ratio of DBS: II: DCBS was 1 3 * 8: 2. The mixture melted at 207-214 ° C.

Example III

Preparation of a mixture of dibenzylidene sorbitol and di-p-chlorobenzylidene sorbitol

A 50 percent blend was prepared by mixing equal weights of commercially available dibenzylidene sorbitol and di-p-15 chlorobenzylidene sorbitol prepared by the method of Example I.

Examples IV and V

Di-m-tolylidene sorbitol (Example IV) and di-p-tolylidene sorbitol (Example V) described in Japanese Patent No. 20 SHO 53 [1978] - 117044 were prepared from aqueous sorbitol and m-tolualdehyde according to p-tolualdehyde according to the method of Example 1. The respective melting points were 216-219 ° C and 247-248 ° G,

Example VI

Di-m-bromobenzylidene sorbitol was prepared from aqueous sorbitol and m-bromobenzaldehyde according to the procedure of Example 1. The product had a melting point of 247-250 ° C.

Example VII

Bis- (3 4-dichlorobenzylidene) sorbitol was prepared from water containing sorbitol and 3-4-dichlorobenzaldehyde according to the procedure of Example 1. The melting point of the product was 270 ° C. Example VIII

Di-o-chlorobenzylidene sorbitol was prepared and purified according to the procedure of Example I to obtain a white solid, mp 220-222 ° C. Incorporation of this product in polypropylene at 0.5% gave a haze value of 50 Example IX

Di-p-methoxybenzylidene sorbitol was prepared and purified according to the procedure of Example I to obtain a white solid 40, mp 185-187 ° C. Recording this 81 0 2 0 1 2 * 7 *

polypropylene product with 0.5% gave a haze value of 52 · Example X.

Di-p-fluorobenzylidene sorbitol was prepared and purified according to the procedure of Example X to obtain a white solid, m.p. 21-218 ° C. Incorporation of this product into 0.25% polypropylene gave a haze value of 17 Example XI

Additives prepared according to the previous examples were incorporated into polypropylene by first preparing a concentrate containing the desired additive ratio (either 5 75 g for a 0.25 percent concentration or 7 50 g for a 0.5 percentage concentration) in 150 g of a commercially available polypropylene and mix in a laboratory mixer. Additional amounts of polypropylene powder (1350 g) were then added to the concentrate while stirring at about 700 rpm in a Welex mixer until the desired additive concentration was reached, for example, either 0.25 wt.% Or 0.5 wt. .yy as indicated in the table. Then the mixture was extruded at 240 ° C, granulated and formed into thin sheets of about 1.27 mm at 250 ° C.

Turbidity and brightness values were measured according to the ASTM standard test method D1003-61 nHaze and luminous transmittance of transparent plastics ”.

8102012 8

Table

Prefix Concentrate Blurry tration no. _ - (#) (%) {%) none 72 dibenzylidene sorbitol 0.25 16 75 / 0.25 10 79 0.38 9 I di-p-chlorobenzylidene -. 0.50 8 sorbitol 0.75 9 -1.00 10 II O-benzylidene-O-p-chlorobenzylidene sorbitol 0.25 11 77 III mixture of dibenzylidene sorbitol and di-p-chlorobenzylidene sorbitol. 0.25 12 IV di-m-tolylidene sorbitol 0.25 12 76 V di-p-tolylidene sorbitol 0.25 13 76 VI di-m-bromobenzylidene sorbitol 0.50 11 VII bis- (2,3-dichlorobenzylidene sorbitol 0 50 8 VIII di-o-chlorobenzylidene sorbitol 0.50 50 IX di-p-methoxybenzylidene sorbitol 0.50 52 X di-p-fluorobenzylidene sorbitol 0.25 17 81 0 2 0 1 2.

*. * 9

As exemplified in the Table, compounds j substituted with one or both of the meta and para positions with either chlorine or bromine atoms exhibit a significant reduction in cloudiness or increase in brightness in polypropylene samples other than those provided with any known brightness promoter. including dibenzylidene sorbitol, which is currently commercially available, and even di-m-tolylidene sorbitol and di-p-tolylidene sorbitol described in Japanese Patent Specification 10 in Example IV. The mixed acetal of Example II further shows an unexpected haze reduction above the haze expected from a compound containing a benzylidene moiety and a p-chlorobenzylidene moiety.

A priori it would be expected that the compound of Example II would exhibit a haze value between dibenzylene sorbitol and di-p-chlorobenzylidene sorbitol. However, the compound exhibits a haze value much closer to that of di-p-chlorobenzylidene sorbitol. Also, the mixture of Example III shows a reduction of turbidity out of proportion to the concentration of the two components. For example, with a composition of 30% by weight dibenzylidene sorbitol and 50% by weight di-p-chlorobenzylidene sorbitol, the expected haze value should be midway between that of the two pure components.

Instead, the mixture gives a reduction greater than 2p than expected.

8102012

Claims (7)

1 · Polyolefin plastic composition with improved transparency, characterized by the presence of a polymer selected from aliphatic polyolefins and copolymers containing at least one aliphatic olefin and one or more ethylenically unsaturated aliphatic comonomers and at least one di-acetal of sorbitol, . . which di-acetal of sorbitol has the structural formula of the formula sheet wherein E, E ^ * E ^ »and E ^ are selected from hydrogen, alkyl with a small number of carbon atoms, 0 'hydroxy, methoxy, mono- and di-alkylamino, amino, nitro and halo - '- «* none, with the proviso that at least one of the symbols E, E, E, and E is chlorine or bromine. - 2 3 4 2. A composition according to claim 1, characterized. k, that the di-acetal di-p-chlorobenzylidene sorbitol, di-m-% chlorobenzylidene sorbitol, O-benzylidene-On-chlorobenzylidene sorbitol, di-m-bromobenzylidene sorbitol or bis (3,4-dichlorobenzylidene) ) is sorbitol. 3. A composition according to claim 1, characterized in that the aliphatic monoalkene is selected from the group 20 consisting of ethylene, propylene, copolymers of ethylene and propylene and 1-butene. i +. Composition according to claims 1 to 3, characterized in that the deacetal is present in the polymer in substantially pure form. A composition according to claims 1 to if, characterized in that the deacetal is present in the form of a mixture with dibenzylidene sorbitol. 6. Composition according to claims 1 to 5, characterized in that a plasticizer is also present selected from the group consisting of dioctyl phthalate, dibutyl phthalate, dioctyl sebacate and dioctyl adipate. : ___ 7 · Polyolefin plastic composition with improved transparency. Characterized by the presence of at least one homopolymer of an aliphatic monoalkene or a copolymer of a 35'-aliphatic monoalkene containing 2 to about 6 carbon atoms and one or more ethylenically unsaturated aliphatic comonomers, which copolymer has been prepared by polymerizing the monoalkene with the comonomer and having an average molecular weight of from about 10,000 to about 500,000 and having at least one deacetal of sorbitol such as di-p-chlorobenzylidene sorbitol, di-m-chlorobenzylidene sorbitol, 0-ben-81 0 2 0 1 2 s. Zylidene-On-chlorobenzylidene sorbitol, di-m-bromobenzylidene sorbitol or bis- (5i-4-dichlorobenzylidene) sorbitol, the amount of the diacetal being about 0.01 to about 2% by weight based on the total weight of the composition. 8. A composition according to claim 7, characterized in that the aliphatic monoalkene is selected from the group consisting of ethylene, propylene, 1-butene and methylpentene. Composition according to claim 8, characterized in. that the di-acetal is di-p-chlorobenzylidene sorbitol. 8102012 V R H — C — Ό / \ I R R H — C — OH H — c — OH H> 81 02 0 1 2