CN1004076B

CN1004076B - Production method of β-crystalline polypropylene

Info

Publication number: CN1004076B
Application number: CN85100465.2A
Authority: CN
Inventors: 史观一; 张景云; 金禾生; 曹友虹
Original assignee: Shanghai Institute of Organic Chemistry of CAS
Current assignee: Shanghai Institute of Organic Chemistry of CAS
Priority date: 1985-04-01
Filing date: 1985-04-01
Publication date: 1989-05-03
Also published as: DE3610644A1; CN85100465A; JPS61281105A; JPH0784502B2

Abstract

The present invention belongs to a production method of beta-crystal form polypropylene. The beta-crystalline polypropylene has high purity and high stability, the content of the beta-crystalline polypropylene can reach 85-93%, the beta-crystalline polypropylene is obtained by mixing polypropylene and a bi-component beta-crystalline nucleating agent in a molten state and performing melt crystallization, and the bi-component nucleating agent is composed of binary acid and oxide, hydroxide or salt of IIA group metal elements in a periodic table. The beta-crystal form polypropylene can be used for manufacturing high-impact injection molding, extrusion products, silk, microporous membranes and the like.

Description

Production method of alpha-crystal form polypropylene

The invention relates to a method for producing beta-crystal polypropylene.

Polypropylene can generally be crystallized in several crystalline forms, the alpha or monoclinic form being the most stable and common one, whereas polypropylene in the beta or hexagonal form is present in a very small amount.

The relative content of the beta-form in polypropylene is measured by X-ray diffraction and can be calculated by the following formula:

K=H₃₀₀/H₃₀₀+H₀₄₀+H₁₁₀+H₁₃₀

wherein K represents the relative content of beta crystal form in polypropylene, H₃₀₀Is the height of the strongest diffraction peak of form beta (300), H₀₄₀，H₁₁₀，H₁₃₀The heights of the three strongest diffraction peaks (040), (110), and (130) of the α crystal form, and when the β crystal form is not contained in the sample, K is 0.

In order to obtain polypropylene with higher beta-crystalline content, a small amount of compound acting as a crystal nucleus, which is called beta-crystalline nucleating agent, needs to be added in the production process for preparing beta-crystalline polypropylene. The nucleating agent currently recognized as being the most effective is quinacridone, the dye permanent red E3B. But the content of beta-form obtained by crystallization in the presence of the nucleating agent is less than 60% under normal conditions (W.Ullmann and J.H.Wendorfy, Progr.Colloid Polymer Sci, 66, 25-33 (1979)). Separately reported that the beta-form content can reach 85% (P.Forgacs, B.F.Tolochka and M.A.Sheromov, Polymer Bulletin, 6, 127-. The beta-crystal polypropylene with the content of 85 percent is difficult to obtain by taking the dye permanent red E3B as a nucleating agent, and the obtained beta-crystal polypropylene product has color and poor thermal stability and is easy to be converted into alpha crystal. Japanese patent publication No. Sho 57-172943 discloses that quinacridone compounds are added to propylene polymerization catalysts, and after polymerization, they are melt-extruded and crystallized at a cooling rate of 10 ℃/min, and the content of beta-form thereof is 63-88% by DSC method. The DSC method is not a standard method for measuring the content of the beta-form, and the method requires that the polypropylene is crystallized under the condition of slow cooling at 10 ℃/min, so that the method is far from the actual production condition and has great limitation. Therefore, the content of the β -form reported in this patent publication is questionable, and the product is red in color and has poor stability.

The invention aims to provide polypropylene with high beta-crystalline form content and good stability, and also provides a method for producing beta-crystalline form polypropylene by using a bi-component compound as a beta-crystalline form nucleating agent. In the presence of the nucleating agent, the polypropylene with beta-crystalline form content can be obtained under the general conditions. The invention also aims to provide a beta-crystalline polypropylene product with higher impact strength, a microporous membrane prepared from the beta-crystalline polypropylene, and the like.

The beta-crystal form polypropylene provided by the invention has a beta-crystal form content as high as 93 percent, namely a K value of 0.93, usually between 85 and 93 percent, which is measured by an X-ray diffraction method, is nontoxic, and has the same appearance and color as the raw materials.

The production process of beta-crystal form polypropylene includes pre-mixing polypropylene and double component beta-crystal form nucleating agent in certain proportion, mixing in molten state and crystallization in molten state in the presence of the nucleating agent. The melt processing temperature is between 180 ℃ and 300 ℃, generally controlled between 200 ℃ and 220 ℃, and is dependent on the molecular weight or melt index of the polypropylene resin, and also related to the processing and molding method. The melt mixing of the polypropylene and the nucleating agent can be accomplished in a single screw extruder, and commercial granular resins can be used as raw materials.

The beta-crystal nucleating agent provided by the invention is prepared by mixing a component A and a component B. The component A is organic dibasic acid, such as pimelic acid, azelaic acid, o-, p-and m-phthalic acid. Component B is II of the periodic Table_AOxides, hydroxides and salts of organic and inorganic acids of group metal elements, wherein the metal elements can be magnesium, calcium, strontium and barium. The salt of organic and inorganic acid can be stearic acid or carbonic acid. The amount of component A is in the range of 0.0001 to 5% by weight, preferably 0.01 to 1% by weight, and the amount of component B is in the range of 0.001 to 5% by weight, preferably 0.05 to 1% by weight, and when used, A and B are added to the polypropylene resin.

The beta crystal form polypropylene can be used for manufacturing various polypropylene products, micropores are generated simultaneously when the beta crystal form polypropylene is stretched and converted into an alpha crystal form, and microporous membranes can be manufactured, wherein the various polypropylene products comprise:

1. high impact resistant articles which may be injection molded products, pipes, sheets or bars, having a beta crystalline polypropylene content of > 85%.

2. The film may be roughened film for power container, printable film and microporous film for ultrafiltering.

3. Fibers, filaments, ropes, and the like. Has the advantages of softness and easy dyeing.

The beta crystal form polypropylene is nontoxic, has the same appearance and color as raw material resin, has high thermal stability, and can not be converted into alpha crystal form after being placed for a long time at the melting temperature. Even if crystallized at slow or fast cooling or at higher temperatures during melt processing, the resulting product does not crack at room temperature and does not break with ductility during stretching, whereas typical polypropylene resins break easily under the above conditions. The mechanical properties of the beta-crystal form polypropylene prepared by the invention at room temperature are superior to those of the alpha-crystal form, and the numerical values are listed in tables 1 and 2.

TABLE 1 mechanical properties of alpha and beta crystalline polypropylene at 23 deg.C

TABLE 2 notched impact strength of alpha and beta crystalline polypropylene at 23 deg.C

From table 1 and table 2, it can be seen that the beta crystalline form polypropylene has higher impact strength and lower yield strength compared with the same grade of alpha crystalline form.

Example 1

Uniformly mixing 100 parts of granular polypropylene homopolymer, 0.1 part of azelaic acid and 0.1 part of powdered calcium carbonate, heating in a single-screw extruder, melting and mixing, then extruding, cooling and granulating to obtain the beta-crystal form polypropylene master batch. After the master batch is subjected to melt processing, polypropylene mainly containing beta crystal forms can be obtained, the content of the polypropylene is slightly different with crystallization conditions, and the K value is 0.85-0.93.

Example 2

Replacement of azelaic acid by pimelic acid, with the conditions as in example 1, a content of polypropylene of the beta crystalline form (in K) of > 0.90 was obtained.

Example 3

The beta nucleating agent in the example 1 is replaced by 0.1 part of terephthalic acid and 0.1 part of calcium oxide, and the example 1 is repeated to obtain the beta-crystalline polypropylene with the content (in K value) of 0.85.

Example 4

Example 1 was repeated using an ethylene-propylene block copolymer instead of the homo-polypropylene in example 1, and the content (in terms of K value) of the obtained beta-form polypropylene was 0.85 to 0.93.

Example 5

The experiment of example 1 is repeated with 0.1 part azelaic acid and 0.1 part barium oxide as nucleating agent, and the content (in K value) of the beta-crystalline polypropylene is 0.70-0.93.

Example 6

The beta-crystal polypropylene master batch prepared in the example 1 is extruded into a flat film by a flat film machine, then cooled and stretched in a single direction or a double direction at the temperature of 60-150 ℃. After stretching, the flat film is converted into a milky microporous film, the density is reduced, and then the film is subjected to heat setting to stabilize the pore structure. The film thus obtained had a whiteness of 95% and could be printed with an oil-based ink.

Claims

1. A method for producing β-crystalline polypropylene containing a two-component β-crystalline nucleating agent, characterized in that polypropylene and the nucleating agent are mixed, wherein the nucleating agent component A is an organic dibasic acid or a salt thereof, wherein the organic dibasic acid can be ortho-, para- or meta-substituted phthalic acid, or an aliphatic dibasic acid of the molecular formula C _n H _2n (COOH) ₂ , where n=C ₁ -C ₁₀ ; the component β is an alkaline earth metal compound of Group II of the periodic table, the content of component A is 1×10 ^-4 5% by weight of the polypropylene, and the content of component B is 1×10 ^-3 5% by weight of the polypropylene, followed by melt processing at a melting temperature of 180-300°C.

2. The method for producing β-crystalline polypropylene according to claim 1, wherein the component B is an alkaline earth metal oxide of Group II of the periodic table, such as magnesium oxide, calcium oxide, or barium oxide.

3. The method for producing β-crystalline polypropylene according to claim 1, wherein the component B is a carbonate of an alkaline earth metal of Group II of the periodic table.

4. The method for producing β-crystalline polypropylene according to claim 1, wherein the component B is a stearate of an alkaline earth metal of Group II of the periodic table.

5. The method for producing β-crystalline polypropylene according to claim 1, wherein the content of component A of the two-component β-crystalline nucleating agent is 1× ^10-2-1 % by weight of the polypropylene, and the content of component B is 0.2-1% by weight of the polypropylene.

6. The method for producing β-crystalline polypropylene according to claim 1, wherein the melting temperature is 200-220°C.