JPH02185505A - Purification of modified polyolefin - Google Patents

Abstract

PURPOSE:To remove unreacted maleic anhydride and by-products of the reaction and to improve hygienic qualities by immersing a maleic anhydride-modified polyolefin graft-modified in a molten state in a carbonyl-contg. 6C or smaller solvent and treating it therein at a specified temp. CONSTITUTION:100 pts.wt. pelletized maleic anhydride-modified polyolefin graft- modified in a molten state is immersed in 100-3,000 pts.wt. 6C or smaller solvent contg. a carbonyl group (e.g. methyl ethyl ketone) and purified in a temp. range of (Tmp-1.1N<2.4>)-(0.7XTmp-0.8N<2.4>) [Tmp is melting peak temperature; N is a number of carbon atoms of the solvent] for 30min to 3hr to remove unreacted maleic anhydride and by-products of the reaction and to obtain a modified polyolefin contg. 0.01-15wt.% maleic anhydride-derived groups.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Application Field The present invention is directed to a modified material having good adhesion to metals or plastics such as polyamide, polyethylene terephthalate, saponified ethylene-vinyl acetate copolymer, polypropylene, and polystyrene. The present invention relates to a polyolefin purification method. The polyolefin obtained using the purification method of the present invention becomes an excellent adhesive material for multilayer laminates, and also has excellent hygiene properties since unreacted maleic anhydride and reaction by-products are not present.

(2) Prior Art Methods for producing maleic anhydride grafted polyolefins include a solution method and a melt method. Among them, a melt method in which a mixture of polyolefin, maleic anhydride, and a radical initiator is melt-kneaded using an extruder and graft polymerized is widely used industrially.

The method for removing unreacted maleic anhydride and reaction by-products present in these maleic anhydride grafted polyolefins is as follows: - After solution graft polymerization, the polymerization solution is cooled and reprecipitation treatment is performed using acetone at room temperature. A method of repeatedly washing unreacted maleic anhydride with acetone (
Special Publication No. 52-32654.

(Japanese Patent Publication No. 44-15422), ■ A method in which maleic anhydride-grafted polyolefin is sprayed with pressurized steam and washed to remove unreacted maleic anhydride, ■ After dissolving the maleic anhydride-grafted polyolefin, an emulsion is created and the unreacted maleic anhydride is removed by washing with water. Method for removing reacted maleic anhydride (JP-A-61-266411)
, ■ A method for removing polyolefins and unreacted maleic anhydride using an aromatic solvent that is a good solvent (Japanese Patent Application Laid-Open No. 1989-1999)
．． -99193) Party is known.

All of the above methods (1) and (2) have the disadvantage that the purification process is expensive because they are dissolved in a solvent during the graft polymerization or purification process. Regarding (2), if the particle size of the graft-modified resin is large, the removal efficiency is not sufficient.

It also has the disadvantage that the grafted maleic anhydride group opens the ring. (2) removes unreacted maleic anhydride without substantially dissolving the polyolefin, but since it is essentially a good solvent for polyolefin, it has the disadvantage that polyolefin may dissolve if the temperature control in the purification process is insufficient. .

(3) Problems to be Solved by the Invention The present invention overcomes the above-mentioned drawbacks of the prior art and efficiently removes unreacted maleic anhydride and reaction by-products that are present in maleic anhydride-modified polyolefins and deteriorate the performance of the product. The aim is to provide an efficient and economical method for purification and removal.

(4) Means for Solving the Problems As a result of intensive research, the present inventors discovered that the above problems could be solved by a method based on the following points, and arrived at the present invention.

That is, when purifying a modified polyolefin that has been graft-modified using maleic anhydride in a molten state, a solvent having a carbonyl group having at most 6 carbon atoms should be used. 7
xTmP 0.81'J2.4)℃ (However, T m
Purification of a modified polyolefin, characterized in that unreacted maleic anhydride and reaction by-products are removed from the polyolefin in a temperature range in which p represents the melting peak temperature (°C) of the polyolefin and N represents the number of carbon atoms in the solvent. This method is particularly effective when the modified polyolefin to be purified is in the form of pellets.

The polyolefins used in the present invention include ethylene, propylene, 1-butene, ]hexene, 3
- A homopolymer of olefins such as methyl-1-pentene, or a random or block copolymer with two or more of these olefins, or a mixture containing these olefins as the main component and vinyl acetate, acrylic acid, methacrylic acid,
It is a copolymer with acrylic ester, methacrylic ester, etc. Specifically, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, ethylene-propylene random copolymer, ethylene-vinyl acetate copolymer, ethylene-butene-1 copolymer, propylene-butene-1 1 copolymer, ethylene-acrylic acid ester copolymer, zinc salt of ethylene-methacrylic acid copolymer, and the like. These may be used alone or in combination of two or more. A commonly known method can be used to graft-modify maleic anhydride in a molten state onto a polyolefin. For example, a method may be used in which a mixture of polyolefin, maleic anhydride, and a radical initiator is melt-kneaded using an extruder and graft polymerized (Japanese Patent Publication No. 126450/1983).

The solvent should be one that has a carbonyl group with at most 6 carbon atoms. T m p -0.8N2.4) °C
unreacted maleic anhydride and reaction by-products are removed from the polyolefin in a temperature range of 0.7'xTmp'-0.8N2.4)°C. If the temperature exceeds this range, the removal of unreacted anhydride maleic and reaction by-products remaining in the modified polyolefin may not proceed efficiently, or the polyolefin may become melted together, making purification difficult. The solvent used in the present invention is a good solvent for the component to be removed, but is a poor solvent for the polyolefin. However, as the number of carbon atoms in the solvent increases, the affinity for polyolefins increases, so the inventors have discovered that the relational expression described in the present invention is necessary, leading to the present invention. Melt bonding does not occur unless the removal temperature exceeds the temperature described in this invention. In particular, the preferred temperature range is (0,97xTmp-
0,8N2.4)℃~(0,73x Tm p -0,
8N2.4) °C. When the number of carbon atoms exceeds 6, the affinity with polyolefins increases, resulting in increased solubility and purification becomes virtually impossible.

Specific examples of solvents having a carbonyl group having at most 6 carbon atoms include acetaldehyde, propanal, acetone, butanal, ethyl methyl ketone, pentanal, diethyl ketone, methyl propyl ketone, methyl acetate, and ethyl acetate. , dimethyl formaldehyde, dimethyl acetaldehyde, etc. In terms of odor, dimethylformamide and dimethylacetaldehyde are preferred. Although odor problems exist, ethanal, propanal, and butanal are preferred if the purification process is complete. Moreover, from the point of view of economy, acetone and ethyl methyl ketone are preferable. The carbonyl group-containing solvent is used in an amount of 100 to 3,000 parts by weight per 100 parts by weight of the modified polyolefin graft-modified using maleic anhydride.

It is necessary to sufficiently soak the modified polyolefin, and furthermore, since the modified polyolefin contains a solvent in which unreacted maleic anhydride and reaction by-products are dissolved, the remaining amount does not substantially affect the process. It is desirable to use 1000 to 2000 parts by weight. Alternatively, performing the above purification twice or more is very effective in reducing the amount of unreacted maleic anhydride and reaction by-products that remain dissolved in the solvent impregnated into the purified modified polyolefin. In this case, purification is possible with a much smaller amount of solvent than the above-mentioned preferred range. In the purification step, it is preferable to carry out stirring or the like in order to effectively bring the solvent into contact with the modified polyolefin and purify it. Further, the purification time may be about 30 minutes to 3 hours. Subsequently, solid-liquid separation is performed by a known method such as traversal separation or centrifugation, and purification can be completed by performing reduced pressure or heat drying.

The shape of the modified polyolefin to be purified is not particularly limited, and raw materials in the form of powder, flakes, and pellets can be used. However, the method of the present invention is most suitable for handling pelleted raw materials. By appropriately selecting the solvent and temperature conditions of the present invention, effective purification can be achieved even using pelleted raw materials, which could only be purified incompletely by conventional methods. Therefore, steps such as solid-liquid separation, transportation, and drying are simplified, and purification can therefore be carried out economically.

Furthermore, in a step before drying the modified polyolefin, a necessary resin stabilizer can be dissolved in a solvent such as acetone, added to the modified polyolefin, and dried. According to this method, it is possible to prevent deterioration of the resin during the drying process, and very favorable results can be obtained in terms of the hue, etc. of the modified polyolefin.

In this way, the group derived from maleic anhydride that the obtained modified polyolefin has is 0.01 to 15% by weight,
Preferably it is O, 1 to 10% by weight. This modified polyolefin can be used alone or diluted with an unmodified polyolefin. It can also be blended with other thermoplastic resins such as rubber, polyamide, and saponified products of ethylene-vinyl acetate copolymer to produce adhesive resins, coating resins, dispersants for inorganic fine powders and pigments, and interface reinforcing materials for polymer alloys. It can be used as

(5) Examples The present invention will be explained in more detail below using Examples.

(Manufacture of modified polyolefin) 100 parts by weight of polypropylene powder (MFR: 0.8) was mixed with 1.0 parts by weight of benzoyl peroxide. 0 parts by weight, 1 part maleic anhydride
．． After adding 5 parts by weight, mix in a Henschel mixer,
(Lmmφ, L/D28 with vented extruder
It was extruded at ℃ and pelletized after cooling with water. The modified polypropylene obtained here was dissolved in boiling xylene, and then reprecipitated using acetone. After thoroughly washing with acetone,
Drying was carried out under reduced pressure at 0° C. for 12 hours, and the amount of maleic anhydride-based groups grafted onto polypropylene was determined to be 0.67% by weight using infrared absorption spectroscopy. The J and G groups on maleic anhydride before dissolving in xylene are 1.26
% by weight. Tm was 159°C. (A) Modified polyolefins shown in Table 1 were obtained under similar conditions.

(Purification of modified polyolefin) Example 1 5 kg of modified polyolefin A pellets and 10 kg of ethyl methyl ketone were placed in a 201 pressure-resistant container equipped with a stirrer, and 1
After stirring at 20° C. for 1 hour, the mixture was cooled to room temperature, and the ethyl methyl ketone solvent was drawn out from the bottom. The ethyl methyl ketone solvent was colored reddish brown. Again, 7 kg of fresh ethyl methyl ketone was added, and the mixture was stirred at 120°C for 1 hour, then cooled to room temperature, and 1]- of the ethyl methyl ketone solvent was drawn out from the bottom. The ethyl methyl ketone solvent was slightly reddish brown in color. Furthermore, 7 kg of fresh ethyl methyl ketone was added, and after stirring at 120° C. for 1 hour, the mixture was cooled to room temperature, and the ethyl methyl ketone solvent was drawn out from the bottom. Thereafter, 300 ml of acetone containing 20 g of Irganox 1076 (manufactured by Ciba Geigy) was added, and the mixture was dried under reduced pressure at 50° C. for 48 hours to obtain pellets with high whiteness. There are no groups based on maleic anhydride in the modified polyolefin (a) obtained after the above treatment.
．． It was 67% by weight, which was in good agreement with the xylene reprecipitation results shown above. The temperature used in this experiment was within the range of 137°C and 89°C, which is the value calculated from the formula shown in the present invention.

Examples 2-4 Using modified polyolefin B and acetate 125
The same procedure as in Example 1 was carried out except that the temperature was 0.degree.

The modified polyolefin (b) obtained after the above treatment contains 0.81% by weight of groups based on maleic anhydride,
This was in good agreement with the xylene reprecipitation results shown above. The temperature used in this experiment was within the range of 137°C and 92°C, which is the value calculated from the formula shown in the present invention. (Example 2) The same procedure as in Example 1 was carried out except that modified polyolefin C and acetone were used and the temperature was 115°C. The modified polyolefin (C) obtained after the above treatment contained 0.34% by weight of groups based on maleic anhydride, which was in good agreement with the xylene reprecipitation results shown above. The temperature used in this experiment is calculated from the formula shown in the present invention (l
lt, within the range of 121°C and 81°C. (Example 3
) The same procedure as in Example 1 was carried out except that modified polyolefin D and ethyl methyl ketone were used and the temperature was 75°C. The modified polyolefin obtained after the above treatment (
d) contains 0.33% by weight of groups based on maleic anhydride.
This was in good agreement with the xylene reprecipitation results shown above. The temperature used in this experiment was within the range of 81°C and 50°C, which is the value calculated from the formula shown in the present invention. (Example 4) Example 5 20g of Irganox 1076 (manufactured by Ciba Geigy)
The same procedure as in Example 1 was conducted except that 300 ml of acetone was not added. There are no groups based on maleic anhydride in the modified polyolefin (f) obtained after the above treatment.
It was 67% by weight, which was in good agreement with the xylene reprecipitation results shown earlier.

The purification temperature used in this experiment was within the range of 137-89'C, which is the value calculated from the formula shown in the present invention.

Comparative Examples 1 and 2 The same procedure as in Example 1 was carried out except that the purification temperature was 70°C. The modified polyolefin obtained after the above treatment (
e) contains 1.10% by weight of groups based on maleic anhydride.
It was recognized that there was almost no purification compared to the results of xylene reprecipitation shown above. (Comparative Example 1) The process was carried out in the same manner as in Example 4 except that the purification temperature was 100°C. The modified polyolefin was completely melted and adhered to the stirring shaft as a lump, and could not be handled as pellets at all. Ta. (Comparative Example 2) (Evaluation of Adhesion) The modified polyolefin obtained in this experiment and the polyolefin obtained in Examples and Comparative Examples were diluted with the same type of resin until the amount of modified polyolefin was 20% by weight. . Furthermore, the MFR of the same type of resin was selected so that the MFR of the finished modified polyolefin composition would exhibit T-die moldability. Adhesive performance was evaluated using a two-layer coextrusion molding machine of 40 mm and 45 mm using ethylene and vinyl alcohol copolymer (ethylene content: 32 mol%) at a die temperature of 220°C and a chill roll with water flowing through it. Two types of two-layer films were made using the following, and a 180 degree peel test was performed at a peel rate of 200 mm and 7 minutes. The results are shown in Table 2. Clearly, the adhesion of well-purified systems is superior.

Furthermore, when comparing Example 1 and Example 5, Example 1 containing an antioxidant had better adhesive properties and a better hue.

(Left below) (6) Effect The modified polyolefin purified by the method of the present invention exhibits good adhesive performance and can be usefully used as an interlayer adhesive layer of various multilayer films. Moreover, since there are few reaction by-products, the hygienic property is also excellent, and it can be suitably used for food applications.

On the other hand, it provides an economical method for producing modified polyolefins.

Claims (2)

[Claims] (1) When purifying a modified polyolefin that has been graft-modified using maleic anhydride in a molten state, a solvent having a carbonyl group having at most 6 carbon atoms is used (Tmp-1.1N^2^.^ 4)℃ to (0.7x
Tmp-0.8N^2^. ^4) It is characterized by removing unreacted maleic anhydride and reaction by-products from the polyolefin in a temperature range of ℃ (where Tmp is the melting peak temperature of the polyolefin (℃) and N is the number of carbon atoms in the solvent). A method for purifying a modified polyolefin. (2) The method for purifying a modified polyolefin according to claim (1), wherein the modified polyolefin to be purified is in the form of pellets.