JPH04209605A - Improved process for production of chlorinated polyolefin - Google Patents

Abstract

PURPOSE:To produce a chlorinated polyolefin excellent in the uniformity of chlorination and heat stability in a high-temperature reaction by using a slurry of a specified pretreated powdery polyolefin and chlorinating the polyolefin by an aqueous suspension process. CONSTITUTION:A process for producing a polyolefin by an aqueous suspension process, wherein the starting solution is a slurry prepared by previously wetting a powdery polyolefin (an alpha-olefin homopolymer, an alpha-olefin copolymer, or a copolymer of an alpha-olefin with an acrylic ester or vinyl acetate) with a water-soluble acrylic polymer/surfactant mixture and dispersing the wetted polymer in an aqueous hydrochloric acid solution. According to this process, the polymer can be kept in a well-dispersed state, does not block during chlorination by an aqueous suspension process and therefore can be uniformly chlorinated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved method for producing chlorinated polyolefins.

(Prior technology) Currently, the methods for producing chlorinated polyolefins include gas phase chlorination method,
A chlorination method in a solvent and a chlorination method in an aqueous suspension have been reported. The gas phase chlorination method is not a common method due to reasons such as the thermal stability of the product, the coloring, and the limited use.

In the chlorination method in a solvent, relatively uniform chlorinated polyolefin can be obtained because chlorination is carried out in an inert chlorine-based solvent mainly composed of carbon tetrachloride. In order to chlorinate a high molecular weight substance, the reaction system becomes highly viscous, and the reaction system dissolves the polyolefin.
The drawback is that the reaction must be carried out at low polyolefin concentrations. This method is used to produce solvent-soluble relatively low molecular weight chlorinated polyolefins used in paints, adhesives, and the like. Furthermore, it is becoming increasingly difficult to use carbon tetrachloride due to air pollution problems.

On the other hand, it is desirable to carry out the chlorination reaction under aqueous suspension, which leads to a blocking phenomenon of the polyolefin particles during the reaction.

Many attempts to use various dispersants have been reported as a preventive measure against this problem. For example, copolymers of polyvinyl alcohol, polyacrylic acid, maleic anhydride and methyl vinyl ether or styrene.

Using polyacrylamide, polyvinylpyrrolidone, etc.
issue.

JP-A-54-124096, etc.). There are also examples of adding surfactants. In the currently reported method, these dispersants and surfactants are dispersed in water and then the polyolefin is dispersed, which results in a lot of foaming due to initial stirring of the reaction, and the polyolefin particles are light and have poor water wettability, so the reaction vessel Floating in large quantities in the upper layer of the water. Therefore, it is chlorinated while being attached to the gas phase wall at the gas-liquid interface in the reaction tank in a band-like manner, and blocking substances are repeatedly desorbed and attached during the process. In addition, due to the poor water wettability of polyolefin particles,
If non-uniform particles remain in the initial stage and are chlorinated as they are, they will be included in the reaction product as perchlorinated products or coarse particles.

After the reaction is complete, the blocking particles and the additives that have entered the inside of the perchlorinated particles during the neutralization of the by-product hydrochloric acid cannot be sufficiently neutralized and washed, resulting in coloration of the chlorinated polyolefin and a decrease in thermal stability. Leads to. These problems have not yet been fully resolved, and currently, in order to prevent blocking, chlorination is carried out at a temperature several tens of degrees lower than the melting point of the raw polyolefin, or chlorination is stopped midway through and the temperature is raised to the melting point of the polyolefin ( (annealing), and methods of lowering the temperature and chlorinating again have been reported.

Other ingredients include titanium dioxide, carbon black, and talc.

Methods to prevent blocking during chlorination using inorganic or organic fine powders such as silica and polychlorinated polychloride have also been reported, but a large amount of these additives remains in the reaction product and may cause problems in the product. It cannot be said to be a practical method as it is subject to usage regulations.

In general, chlorinated polyolefins obtained by the aqueous suspension method have relatively large molecular weights, ranging from tens of thousands to hundreds of thousands.

A wide variety of materials are produced, ranging from rubber-like to plastic-like properties with a chlorine content of 20 to 50% by weight.

These applications include polyethylene and polypropylene.

Molded products for polymer blends such as polyvinyl chloride and ABS resin, or chlorinated polyolefin alone.

It is crosslinked and used for rubber-like molded products, etc., and the desired chlorinated polyolefin is one that is chlorinated as uniformly as possible, has a fine particle shape, and has excellent thermal stability.

(Problems to be Solved by the Invention) In view of the above points, the present invention prevents blocking of polyolefin particles when chlorinating polyolefin by an aqueous suspension method, and achieves excellent thermal stability through uniform chlorination and high temperature reaction. The object of the present invention is to provide a method for obtaining a chlorinated polyolefin.

(Means for Solving the Problems) In other words, when polyolefin is chlorinated by an aqueous suspension method, the present invention wets a powdered polyolefin as a raw material solution with a water-soluble acrylic polymer-surfactant mixture in advance. This is an improved method for producing chlorinated polyolefin, characterized by using a slurry liquid dispersed in an aqueous hydrochloric acid solution.

The polyolefin used in the present invention is a powdered α-
Olefin homopolymers or copolymers, such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, ethylene-acrylic acid ester copolymer, ethylene-vinyl acetate copolymer It refers to a polymer having a crystal structure such as a polymer or an ethylene-butadiene copolymer. Particularly suitable are polyethylene, ethylene-butene copolymers, ethylene-acrylic esters or vinyl acetate copolymers.

The molecular silver for polyolefins is usually io or oo.

~1,000,000 preferably 40,000-300
．． 000 is appropriate. There is no particular limit to the particle size of the polyolefin, but since the chlorination reaction is a heterogeneous one, it is preferable to make it as fine as possible in order to obtain a uniform chlorinated product. Particles of 50 to 1000 ta are usually suitable.

The water-soluble acrylic polymer used in the present invention is a polymer of acrylic acid or acrylic ester, or a copolymer thereof, or an alkali metal salt or ammonium salt of these polymers or copolymers, and has a molecular weight of 3000 or more. In particular, those with a value of 10,000 or more are preferred. The above acrylic ester has 1 to 4 carbon atoms.
Alkyl esters of are preferred. Among these polymers,
Those capable of water soluble or colloidal dispersion are suitable for the present invention.

Surfactants include nonionic or anionic surfactants, such as polyoxyethylene alkyl ethers, polyoxyalkylphenol esters, and polyoxyethylene alkyl esters.

Sorbitan alkyl esters, ethylene oxide
Nonionic activators such as propylene oxide block polymers, anionic activators such as sodium alkylbenzenesulfonates, alcohol sulfates, alkylsulfonic acids, alkylarylsulfonic acids or their sodium salts are suitable.

Addition of an anion-active styrenic polymer is also effective.

According to the currently reported and practiced aqueous suspension method for chlorination, a dispersant and a surfactant are first dissolved in water.
Powdered polyolefin is dispersed in the reactor to carry out the chlorination reaction, but because the polyolefin particles are lightweight and have poor water wettability, the polyolefin particles tend to float or collect in the upper layer of the reactor, causing the air in the container to evaporate. It adheres in a band shape to the gas phase portion of the liquid interface, resulting in poor dispersibility. These factors lead to blocking during the reaction, and heterogeneous chlorination and perchlorination are mixed into the reaction product.

In addition, as the chlorination reaction progresses, the system becomes acidic due to the by-product hydrochloric acid, and the acrylic polymer in particular becomes precipitated particles and disperses throughout the system, so polyolefin particles may have sufficient effect as an anti-blocking agent. Therefore, a large amount is required. - The surfactant and anionically activated styrene polymer are uniformly dispersed even when the system becomes acidic with hydrochloric acid, but as the reaction progresses, the dispersion ability decreases due to the action of by-product hydrochloric acid and hypochlorous acid. I'll come. For this reason, the amount of surfactant used is increased or the surfactant is added during the reaction, but this results in increased foaming of the reaction system, which is not preferable for the reason mentioned above.

The present inventors discovered that the above acrylic polymer completely dissolves in an aqueous system, but is insoluble and precipitates in an aqueous hydrochloric acid solution system.
A detailed study was conducted based on the fact that this method is effective in improving the water wettability of polyolefins, and that even if the acrylic polymer is chlorinated, it can be dissolved and removed in the neutralization washing step with alkali. As a result, by pre-wetting powdered polyolefin with a water-soluble acrylic polymer-surfactant mixture and dispersing this in a 1-30% by weight aqueous hydrochloric acid solution, the acrylic polymer can be efficiently applied to the surface of the polyolefin. The surfactant was dissolved in the aqueous hydrochloric acid solution and worked to help disperse the polyolefin particles, making it possible to obtain a hydrochloric acid slurry of polyolefin with good wettability and dispersibility.

The appropriate concentration of hydrochloric acid in the hydrochloric acid aqueous solution is 1 to 30% by weight, but since the concentration increases due to the by-product hydrochloric acid from the reaction, the concentration should be 3 to 2% by weight.
5% by weight is preferred.

At this time, since the acrylic polymer alone does not have sufficient dispersion ability, it is desirable to use an anionic styrene polymer in addition to a nonionic or anionic surfactant as a surfactant. However, the amount of surfactant used should be as small as possible in order to suppress foaming of the system.

The water-soluble acrylic polymer-surfactant mixture according to the present invention has a solid content of 0.3 to 2.0% of the acrylic polymer, respectively.
0% by weight, surfactant 0.1-2.0% by weight, water 99.
A proportion of 6 to 96.0% by weight is preferred.

Wet processing of polyolefin is performed using a mixer such as a Henschel mixer or a ribbon mixer.
Thoroughly mix 30 to 70 parts by weight of the above-mentioned mixed liquid with respect to the parts by weight to blend the two well. At this time, the wet state of the polyolefin is preferably a state in which the polyolefin is completely wet to a cake-like state, and the emphasis of the present invention is to avoid excess water. If the water content is too high, free acrylic polymer exists and is undesirable.

Next, by gradually adding the polyolefin to the aqueous hydrochloric acid solution while stirring, a finely dispersed polyolefin hydrochloric acid slurry with good wettability can be obtained.

The polyolefin concentration in the hydrochloric acid slurry is preferably 3 to 20% by weight in consideration of stirring during the chlorination reaction. The hydrochloric acid slurry of polyolefin prepared in this way has very good thermal stability even when heated to a high temperature (approximately 130°C) near the melting point of polyolefin, and does not cause abnormalities such as 70° cracking or adhesion to the reactor wall. doesn't happen. Further, even under stirring, there was little foaming and the polyolefin particles were in a good slurry form.

In the method for chlorinating polyolefin according to the present invention, the chlorination reaction is carried out at a temperature 10°C or more lower than the melting point of the raw material polyolefin in order to avoid blocking of polyolefin particles as in conventional methods, and the reaction is carried out at a temperature 10°C or more lower than the melting point of the raw material polyolefin. There is no need to change the temperature in two or three stages, or to perform operations such as annealing at the melting point of the polyolefin during the process.
The chlorination reaction can be carried out in the range of 150'C. For example 1
The chlorination reaction can be started even at a high temperature of 20 to 135°C, and as the reaction progresses, the temperature can be raised up to 150°C due to the heat of reaction.

The slurry-like reaction product, which has been chlorinated to a predetermined chlorine content, is taken out and separated into the reaction product and the reaction solution (hydrochloric acid aqueous solution). The reaction product is neutralized with a 10-48% by weight aqueous solution of caustic soda at air temperature to 100°C, then separated, washed with water at air temperature to 100°C, and dried to produce a chlorinated polyolefin product. -Stearic acid or a salt thereof can also be added to prevent blocking properties of the obtained product.

(Effects of the Invention) According to the present invention, by treating the surface of polyolefin particles with a specific dispersion liquid, a good dispersion state is maintained during chlorination using an aqueous suspension method, and a uniform dispersion is achieved without causing a blocking phenomenon. Chlorination becomes possible. Therefore, since polyolefins can be chlorinated at high temperatures, the reaction rate is increased and the reaction time is significantly shortened. Because it is not subjected to a long thermal history due to the high-temperature, short-time reaction, fine particles almost equivalent to the uniformly chlorinated raw material polyolefin can be obtained, and the by-product hydrochloric acid can be neutralized by the alkali.

Washability with water is very good. Since the acrylic polymer fixed on the polyolefin is soluble in the alkaline solution, it can be almost completely removed in the neutralization cleaning step. The same applies to surfactants.

The chlorinated polyolefin obtained in this way contains very few blocking substances and perchlorinated substances, is uniformly chlorinated, and can be sufficiently neutralized and washed when heated. It is characterized by excellent physical stability.

The chlorination method according to the present invention is particularly suitable for producing a rubbery chlorinated polyolefin free of polyolefin crystals since it can be chlorinated at a high temperature.

(Example) The present invention will be explained below with reference to Examples and Comparative Examples.

All composition percentages and parts in steel are by weight.

Examples 1 to 4 Polyolefins such as polyethylene and polyethylene-7-tene copolymer shown in Table 1 were placed in a ribbon mixer, and the dispersion liquid shown in Table 2 was gradually added with rotational stirring, and mixed in the proportions shown in Table 3. A uniformly wet polyolefin was obtained.

This polyolefin was gradually added to an aqueous hydrochloric acid solution in the proportions shown in Table 3 with stirring and thoroughly dispersed.

The polyolefin hydrochloric acid slurry prepared in this way was mixed with 100. Place in +7 glass lined pressurized reaction vessel,
After raising the temperature to a predetermined temperature with stirring, air purging was performed, and chlorine gas was introduced to conduct a reaction so that the chlorine content was 30 to 40%.

Chlorine gas was introduced from the top of the reaction vessel (top blowing) or from the bottom (bottom blowing). Almost no chlorinated polyolefin was observed to adhere to the inner wall of the reaction vessel after the reaction was completed. Table 3 shows the foaming state, blocking state, chlorination time, etc. during the reaction.

Next, the reaction product and the reaction solution (a mixed solution of the charged hydrochloric acid and the by-product hydrochloric acid) were separated, and the reaction product was neutralized and washed with a 20% aqueous solution of caustic soda in a total of 180 fl under stirring at 50°C. After washing with warm water at 80° C., 1 part of calcium stearate was added to 100 parts of chlorinated polyolefin and dried. As a result, a white fine powder chlorinated polyolefin as shown in Table 4 was obtained.

Comparative Examples 1 and 2 A 100.11 glass-lined pressurized reaction vessel was charged with water and a dispersion liquid in the proportions shown in Table 3, and the polyethylene shown in Table 1 was gradually added while stirring. At this time, Comparative Example 1 had a lot of foaming, and both Comparative Examples 1 and 2 had poor wetting of the polyethylene, so they circulated around the upper layer and had poor dispersibility.

Next, the temperature was raised to 110°C, and after air purging, chlorine gas was introduced from the top of the reaction vessel (top blow) to reduce the chlorine content to 2.
After chlorination to 0%, the temperature was raised to 130° C. without introducing chlorine gas, and annealing was performed for 30 minutes. After cooling to 120° C., chlorine gas was introduced again to conduct a reaction until the chlorine content was 35%. The reason why the initial reaction temperature was set at 110 DEG C. is that if the chlorination reaction is carried out at a temperature higher than this, a blocking phenomenon of polyethylene will occur, which is undesirable.

After the chlorination was completed, a band of polyolefin blocking material was found attached to the wall of the gas phase portion of the reaction vessel.

Neutralization with caustic soda was performed by raising the neutralization temperature to 80° C. because the surface became hard due to the blocking of the chlorinated polyethylene particles and the long-term thermal history caused by the reaction. Post-processes are the same as in the examples.

<Physical property test> Examples 1 to 4. The chlorinated polyolefins of Comparative Examples 1 and 2 were kneaded with two rolls at 130'C for 5 minutes, and the separated sheet was heat-pressed at 150°C and 100K (J/cut) for 10 minutes to form a 150X 150X 2mm thick molded sheet. Table 4 shows the results of various physical property tests performed on the above sheet.

Table 1 Raw material polyolefin Table 2 Water-soluble acrylic polymer-surfactant mixture* Acrylic polymer aqueous solution■ Acrylic acid polymer aqueous solution molecular weight 13,000 Solid content 30%■ Acrylic acid copolymer ammonium salt aqueous solution molecular weight 27 ．．
000 Solid content 30% Surfactant ■ Nonionic surfactant: Polyoxyethylene alkyl phenyl ether ■ Anionic surfactant: Alkylbenzenesulfonic acid sodium salt Active ingredient 30% Table 3 Reaction liquid composition and chlorination reaction table 4 Physical properties test * Hardness: Shore A hardness Thermal stability: PET film (30
M) was pasted and heat pressed at 120°C and 10100k for 5 minutes, then cut into 5cmM (2 pieces thick) and heated at 190°C.
After being left in a gear oven, the appearance of the parts, vessels, and (materials) was examined by color change.

O No discoloration at all O Slight yellowing Δ Yellowing The slurry liquid was stable and the chlorination reaction progressed. In addition, neutralization with alkali was completed in a short time at low temperature, probably because the particles of the reaction product were fine and the particles were relatively porous due to the short thermal history caused by the short reaction time. .

In terms of physical properties, Examples 2 and 3 and Comparative Examples 1 and 2 use the same polyethylene and show almost the same physical properties, but Examples 2 and 3 according to the present invention are superior in thermal stability. I understand.

Claims (2)

[Claims] (1) When polyolefin is chlorinated by the aqueous suspension method, a slurry liquid in which powdered polyolefin is pre-wetted with a water-soluble acrylic polymer-surfactant mixture and dispersed in an aqueous hydrochloric acid solution is used as the raw material liquid. An improved method for producing a chlorinated polyolefin, characterized by: (2) the polyolefin is an α-olefin homopolymer,
The production method according to claim 1, which is a copolymer of α-olefin or a copolymer of α-olefin and acrylic ester or vinyl acetate.