JPS6148536B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyolefin plastic compositions with improved transparency and shrinkage during molding. Polyolefins, such as polyethylene or polypropylene, are formed into films, sheets or hollow articles and have a wide range of applications in the field of packaging and containers. However, the use of the above-mentioned polyolefins has been limited because of their poor transparency. In particular, they were unsuitable for use as packaging materials or containers for items such as cosmetics or foodstuffs for which it is desirable to be able to see the contents from the outside. Attempts have been made to improve the transparency of polyolefins by adding certain additives, such as para-t-butylbenzoic acid and its salts, low molecular weight waxy polyethylene, or Although low molecular weight waxy polypropylenes have been proposed, these conventional additives either degrade the mechanical and/or chemical properties of the product or are incompatible with polyolefins to provide sufficient improvement in transparency. It was something I couldn't get. The present inventor previously discovered that by adding dibenzylidene sorbitol (hereinafter referred to as DBS) to polyolefin, the drawbacks of conventional additives as described above were overcome, and a polyolefin composition with significantly improved transparency was obtained. They discovered that the invention could be obtained and filed a patent application for this invention (Japanese Patent Application No. 94424/1982). However, DBS has a high melting point (approximately 210℃),
Moreover, since the compatibility with polyolefin is not necessarily good, it is common to use a surfactant to uniformly mix it into polyolefin, otherwise it is not easy to achieve uniform mixing. . On the other hand, the surfactants generally do not give favorable results for improving the transparency of polyolefins by DBS. Therefore, an object of the present invention is to provide an additive that does not impair the effect of DBS on the transparency of polyolefin and facilitates uniform mixing of DBS and polyolefin. As a result of research to achieve the above object, the present inventor found that if a small proportion of tribenzylidene sorbitol (hereinafter referred to as TBS) is added to polyolefin together with DBS, DBS can easily be
The present invention was achieved by discovering that TBS is compatibilized and uniformly mixed with polyolefin and does not impair the transparency improvement effect of polyolefin caused by DBS. That is, the present invention provides a resin composition containing as essential components one or more polymers or copolymers of aliphatic monoolefin and dibenzylidene sorbitol, wherein the composition further contains tribenzylidene sorbitol. This composition is characterized by the following. Examples of olefin polymers whose transparency and shrinkage during molding are advantageously improved according to the present invention include aliphatic monoolefins having 2 to 6 carbon atoms with a number average molecular weight of about 10,000 to 200,000, preferably about 30,000. ~
150,000 polymers or copolymers such as polyethylene, polypropylene, crystalline ethylene-propylene copolymers and polymethylpentene. Polyolefins such as those exemplified above are essentially linear regular polymers, optionally with short side chains. DBS used in the present invention contains 1 mol of d
-A white powder with a melting point of 210-212°C obtained by the reaction of sorbitol and 2 moles of benzaldehyde in the presence of an acid catalyst and at elevated temperatures. This thing has the following chemical formula () It is a compound represented by , and there are mainly three types of isomers. The typical structural formula is the following formula ()
It is as follows. TBS used in combination with DBS in the present invention is DBS
can be prepared by reacting an additional 1 mole of benzaldehyde in the presence of an acid catalyst and at elevated temperatures, and is a white powder with a melting point of about 189-191°C. This one has the following chemical formula () The structural formula is as shown in the following formula (). The content of DBS in the composition of the present invention is 0.1 to 0.7% by weight, preferably 0.3 to 0.7% by weight, based on the total amount of the composition.
It is in the range of 0.5% by weight. When the content of DBS is less than 0.1% by weight, sufficient improvement in transparency and shrinkage during molding cannot be obtained. A content of DBS higher than 0.7% by weight does not provide any additional benefits. However, it is possible to contain more than 0.7% by weight. Also, a concentrated composition containing DBS in a large amount up to about 4% by weight,
It can also be used as a masterbatch. On the other hand, TBS is 0.5:95 to DBS in terms of weight.
Used in a ratio of 50:50, preferably 10:90 to 40:60. If the proportion of TBS used is too small compared to DBS, it will be difficult to uniformly mix DBS into polyolefin. There is no particular advantage to using too much TBS. Predetermined amounts of DBS and TBS within the above ranges can be added and mixed separately to the polyolefin in any order. However, it is preferable to add DBS and TBS to the polyolefin at the same time, in which case DBS and TBS can be used as a premix. As a result of previous research on the production of DBS that does not contain the by-product monobenzylidene sorbitol (hereinafter referred to as MBS), the present invention was developed by dehydrating and condensing 1 mol of sorbitol and 2 mol of benzaldehyde in the presence of an acid catalyst. When producing dibenzylidene sorbitol, the reaction is carried out in two stages. In the first stage, the reactants are reacted under heating at a temperature of 50 to 70°C, and the conversion rate of sorbitol to dibenzylidene sorbitol is 10. When ~40% is reached, water and an additional amount of acid catalyst are added to proceed to the second stage, in which at least 2.5 parts by weight per part by weight of sorbitol in the aqueous reaction medium at room temperature. They discovered that by reacting in a suspended state, DBS containing no or almost no MBS could be obtained as an aqueous suspension, and filed a patent application for this method (Japanese Patent Application No. 146587-1987). In the conventional DBS manufacturing method, the generated DBS
Since it contains a considerable amount of MBS, it required extensive purification to remove it.
does not require such purification, and the by-product TBS has a weight ratio of about 10:90 to 35:65 to DBS.
Contains. Therefore, the by-product TBS-containing DBS obtained by this method is suitable for use as is as an additive in the present invention. The composition of the present invention can be obtained by simply adding predetermined amounts of DBS and TBS or mixtures thereof to the olefin polymer or copolymer of the present invention as exemplified above and mixing by any mixing means. The compositions of the invention may contain other additives, such as clear colorants, plasticizers such as dioctyl phthalate, dibutyl phthalate, dioctyl stearate and dioctyl adipate, as long as they do not adversely affect transparency and/or molding shrinkage. agent can be added. The composition of the present invention provides films, sheets and blow molded articles with improved transparency and shrinkage during molding, and excellent mechanical and chemical properties, so that packaging materials and containers for cosmetics and foodstuffs can be used. It is suitable as a material for. The examples set forth below further illustrate the invention. Parts and percentages given in the examples are by weight unless otherwise specified. The transparency (haze value) and molding shrinkage values shown in the examples were obtained by testing according to the following method. (1) Haze value ASTMD1001-59T (2) Shrinkage during molding (shrinkage rate) Test molded by injection molding at a specified injection temperature using a mold with a rectangular parallelepiped cavity with a length of 55 mm and a cross section of 10 mm x 10 mm. Measure the thickness of the piece and calculate it using the following formula. Shrinkage rate = Depth of mold cavity - Thickness of test piece / Depth of mold cavity × 100% Injection molding of the warped test specimen is carried out under the following conditions. Injection temperature Predetermined temperature specified in each example Injection time 5 seconds Holding time 3 seconds Cooling time 40 seconds Mold temperature 80°C Example 1 Number average molecular weight 40000, propylene unit content 90
Add a predetermined amount of a mixture of TBS and DBS at a weight ratio of 20:80 to pellets of mol% ethylene propylene copolymer (Mitsubishi Noblen BC-8, manufactured by Mitsubishi Yuka Co., Ltd.) and inject the mixed resin composition using a blender. Test pieces were made by injection molding at a temperature of 210°C. The composition of the resin composition and the haze value and shrinkage rate of the test piece are shown in Table 1 below.

[Table] Example 2 A predetermined amount of a mixture of TBS and DBS at a weight ratio of 30:70 was added to pellets of polyethylene with an average molecular weight of 20,000 (Sumitomo Polyethylene G806 manufactured by Sumitomo Chemical Co., Ltd.), and the resin composition was mixed with a blender at an injection temperature. Test pieces were made by injection molding at 180°C. The composition of the resin composition and the haze value and shrinkage rate of the test piece are shown in Table 2 below.

[Table] Example 3 (A) Production of DBS containing TBS 212 grams (2 moles) of benzaldehyde, 270 grams (1 mole) of a 70% aqueous solution of D-sorbitol, and 10 grams of p-toluenesulfonic acid were placed in a reaction vessel, and the The reaction is carried out with stirring at a temperature of °C.
The viscosity of the mixture in the reactor gradually increases, and after 30 minutes,
It became jelly-like, and the torque of the stirrer reached about three times the initial torque (first stage). The amount of DBS produced at this point was 20% of the theoretical value. 400 grams of a 10% aqueous solution of hydrochloric acid and 100 grams of water were added to the jelly-like reaction product obtained in the first stage reaction, and the mixture was transferred to the second stage.
The temperature inside the reactor was lowered to 25°C, stirring was continued at this temperature for 6 hours, the resulting suspension was left to age at room temperature for 12 hours, and treated with a 10% aqueous solution of caustic soda to remove the catalyst. DBS white powder (melting point 182
~187°C) 280g was obtained. This one is about 10%
Contains TBS. (B) Production of polyethylene composition A predetermined amount of TBS-containing DBS obtained in (A) above was added to pellets of polyethylene with an average molecular weight of 60,000 (Mitsubishi Novatech ET010 manufactured by Mitsubishi Yuka Co., Ltd.), and the resin composition was mixed in a blender. Test pieces were made by injection molding at an injection temperature of 210℃. The composition of the resin composition and the haze value and shrinkage rate of the test piece are shown in Table 3 below.

【table】

Claims (1)

[Scope of Claims] 1. A resin composition containing one or more polymers or copolymers of aliphatic monoolefins and dibenzylidene sorbitol as essential components, the composition further containing tribenzylidene sorbitol. A composition comprising: 2 The content ratio of dibenzylidene sorbitol to tribenzylidene sorbitol is 99.5 to 0.5 by weight.
A composition according to claim 1, wherein the ratio is ˜50:50. 3 A mixture of dibenzylidene sorbitol and tribenzylidene sorbitol is prepared by subjecting 1 mole of sorbitol and 2 moles of benzaldehyde to a two-step dehydration condensation reaction in the presence of an acid catalyst. When the conversion rate of sorbitol to dibenzylidene sorbitol reached 10-40%, water and an additional amount of acid catalyst were added to proceed to the second stage. The claimed invention is dibenzylidene sorbitol containing tribenzylidene sorbitol obtained by a method of reacting in suspension in an aqueous reaction medium in an amount of 2.5 parts by weight or more per 1 part by weight of sorbitol at room temperature. The composition according to item 1 or 2. 4. The composition according to any one of claims 1 to 3, wherein the aliphatic monoolefin is selected from the group consisting of ethylene, propylene, and methylpentene.