JP2000256420A - Degradation agent for propylene polymer and degradation process of propylene polymer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a degradation agent for propylene polymers which is peroxy bond-free and therefore easy to handle, little in volatilization and yields a propylene polymer having little odor, and a degradation process of propylene polymers. SOLUTION: A degradation agent for propylene polymers comprises a diisopropylbenzene oligomer of the formula (wherein n is a number of from 2 to 50). In a degradation process of propylene polymers, a degradation agent comprising a diisopropylbenzene oligomer of the formula is added to a propylene polymer and the resulting mixture is heated at a temp. from 200 to 300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a propylene polymer having a high decay efficiency for reducing the molecular weight and a low odor, and a propylene polymer degrading agent which does not easily volatilize, and uses the same. The present invention relates to a method for degrading a propylene-based polymer.

[0002]

2. Description of the Related Art A propylene polymer is a material having excellent mechanical properties, but usually has a relatively high molecular weight as it is. Therefore, generally degenerate propylene polymer,
It has been practiced to improve the fluidity by appropriately reducing the molecular weight. As the degradation method, a method of adding a compound that generates a radical to a propylene-based polymer and then heating the mixture using a kneader or the like is generally employed.

[0003] At this time, peroxide is generally used as a compound that generates a radical to lower the molecular weight of the propylene-based polymer (hereinafter, referred to as a degenerating agent).
For example, Japanese Patent Publication No. 44-15186 discloses a method using dicumyl peroxide. However, peroxides can undergo rapid decomposition and require careful handling. In addition, due to the structure, a decomposition product having a peculiar odor such as ketone or alcohol is generated in the degradation reaction process, so that there is a problem that the working environment is deteriorated and the product has odor.

[0004] In order to solve such problems, a method is disclosed in which a compound which does not contain a peroxide bond and generates a radical by cleavage of a carbon-carbon bond is used as a degenerating agent. For example, JP-A-49-99549 discloses a method using 2,3-dimethyl-2,3-diphenylbutane (hereinafter referred to as dicumyl).

[0005]

However, since dicumyl does not have an unstable peroxy bond, it has good handleability. However, its decomposition temperature is high, so that the decomposition reaction can be carried out at 200 ° C. or more. It must be performed at a very high temperature. At such a high temperature, dicumyl volatilizes partially before undergoing radical decomposition, and thus has a disadvantage that the efficiency as a degrading agent is poor. Furthermore, since aromatic volatile compounds such as cumene are produced as a decomposition product of dicumyl, there is a problem that the propylene polymer obtained still has an odor.

The present invention has been made by paying attention to the problems existing in the prior art as described above. The object is to provide a propylene-based polymer degrading agent that does not contain a peroxy bond, is easy to handle, is difficult to volatilize, and can obtain a propylene-based polymer with less odor. is there. Another object of the present invention is to use such a propylene polymer degrading agent to reduce the amount of a propylene polymer which can be efficiently obtained with a moderately degraded odorous propylene polymer. It is an object of the present invention to provide a synthesis method.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, by using a compound having a specific structure as a degrading agent, a degraded propylene-based polymer having a low odor has been obtained. They have found that they can be obtained efficiently and completed this invention.

That is, the propylene polymer degenerating agent of the first invention comprises a diisopropylbenzene oligomer represented by the following general formula (1).

[0009]

Embedded image (In the formula, n represents a number of 2 to 50.) Further, the method for degrading a propylene-based polymer of the second invention is as follows.
The propylene-based polymer is mixed with a propylene-based polymer degenerating agent composed of a diisopropylbenzene oligomer represented by the general formula (1) of the first invention, and heated.

[0010]

Embodiments of the present invention will be described below in detail. The propylene polymer degrading agent is
The diisopropylbenzene oligomer represented by the following general formula (1) is used as an active ingredient.

[0011]

Embedded image In the formula, n represents a number of 2 to 50, preferably 3 to 40. When n is 1, no radical can be generated in the degradation reaction process, so that it does not act as a degenerating agent. On the other hand, if n exceeds 50, the compatibility with the propylene-based polymer deteriorates and the efficiency of the degradation reaction decreases.

The diisopropylbenzene oligomer is obtained by converting diisopropylbenzene into Polymer Science U.S.A. S. S. R. 1, p. 341, 1960, by oxidative condensation using a radical generator such as di-t-butyl peroxide. That is, as diisopropylbenzene as a raw material, m-diisopropylbenzene, p-
-Diisopropylbenzene and mixtures of m-diisopropylbenzene and p-diisopropylbenzene.

When m-diisopropylbenzene is used as a raw material, the diisopropylbenzene oligomer of the general formula (1) is a meta-form, and when p-diisopropylbenzene is used, it is a para-form. On the other hand, m
When a mixture of -diisopropylbenzene and p-diisopropylbenzene is used, it is composed of a meta form and a para form.

The diisopropylbenzene oligomer represented by the general formula (1) may be in an ortho form, but since the ortho form is difficult to produce, it is a meta form or a para form or a mixture of the meta form and the para form. Preferably, there is.

The oxidative condensation is usually carried out while removing low boiling components derived from the decomposition products of the radical generator. The oligomer resulting from the oxidative condensation is usually a polydisperse oligomer having a molecular weight distribution. That is, it is composed of a mixture of a plurality of compounds having different values of n in the general formula (1). In the present invention, the average value of n may be in the range of 2 to 50,
n may contain a component of 1 or a component of more than 50.

Further, diisopropylbenzene in which n is 1 may be contained as a diluent. In such a case, the average value of n may be less than 2. The average value of n can be determined from the number average molecular weight of the oligomer measured by gel permeation chromatography, and the value is represented by a real number including a decimal point.

The oligomer obtained relatively easily by the oxidative condensation reaction can be used as a degrading agent as it is or after being purified by a reprecipitation method.
Further, it can be used in a state diluted with a liquid substance or a solid substance which does not affect the degradation reaction.

Compounds such as diisobutylbenzene oligomers other than the diisopropylbenzene oligomer represented by the general formula (1) are difficult to produce or have too high a thermal decomposition temperature. Unsuitable as a degradant.

Next, a method for degrading the propylene polymer is as follows.
After mixing the propylene polymer with the diisopropylbenzene oligomer represented by the general formula (1) as a degenerating agent,
It is performed by heating.

Examples of the propylene polymer to be degraded include polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, propylene and butene-1, hexene-1,4-methylpentene. 1, random copolymers with α-olefins having 4 to 12 carbon atoms, such as octene-1, and terpolymers to which ethylene is further added.

In the case of an ethylene polymer other than the propylene polymer, a cleavage reaction does not occur even if radicals are generated in the chain, and the radicals in the chain recombine with each other to form a crosslinked product, which has the opposite effect. Not suitable for showing.

The amount of the degrading agent used is propylene-based polymer 1
0.001 part by weight, preferably 0.001 to 1 part by weight,
More preferably, it is 0.005 to 0.5 part by weight. If this amount is less than 0.001 part by weight, the effect of degradation is small,
On the other hand, if it exceeds 1 part by weight, the molecular weight of the obtained propylene-based polymer tends to be too small and mechanical properties tend to decrease.

The propylene-based polymer is degraded in a molten state of the propylene-based polymer using a usual melt-kneading apparatus. Examples of the melt kneading apparatus include a single-screw or twin-screw extruder, a Banbury mixer, a kneader, and a roll.

The diisopropylbenzene oligomer generates radicals by cleavage of a carbon-carbon bond under heating to induce a degradation reaction of a propylene polymer. Therefore, the heating temperature is equal to or higher than the temperature at which the carbon-carbon bond of the diisopropylbenzene oligomer is cleaved to effectively generate radicals, and equal to or lower than the thermal decomposition temperature of the propylene-based polymer. The specific heating temperature is usually 200 to 3
It is in the range of 00C, preferably in the range of 220-300C.

In the method for degrading a propylene-based polymer, a weather-resistant stabilizer,
Additives such as an antioxidant, an antistatic agent, a filler, and a coloring agent may be added as necessary.

Now, with respect to a specific degradation reaction of a propylene-based polymer, for example, the case where n in the general formula (1) is 2 will be described. First, as shown in the following reaction formula (2),
In a diisopropylbenzene oligomer, a benzyl carbon-benzyl carbon bond is radically cleaved by heating to generate a tertiary benzyl radical.

[0027]

Embedded image Next, the generated tertiary benzyl radical abstracts a hydrogen atom of the propylene-based polymer, thereby generating a chain radical in the propylene-based polymer chain. Subsequently, the generated radical in the chain of the propylene polymer causes a self-cleavage reaction, and the propylene polymer is decomposed. Thus, the molecular weight of the propylene-based polymer decreases.

The decrease in the molecular weight of the degraded propylene-based polymer can be attained, for example, by measuring the fluidity of the propylene-based polymer, that is, by increasing the melt index value (MI value) as an index of the fluidity. You can know.

The degraded propylene-based polymer obtained as described above is used as a raw material for, for example, extrusion molding and injection molding. The effects exerted by the above embodiment will be described together.

The propylene polymer degenerating agent of the embodiment does not contain a peroxy bond like conventional dicumyl peroxide, so that it does not have a risk of causing rapid decomposition and is easy to handle.

The propylene-based polymer degenerating agent does not generate odorous decomposition products such as conventional dicumyl peroxide or dicumyl in the degradation reaction process, so that a odorless propylene-based polymer is obtained. be able to.

According to the method for degrading a propylene-based polymer, a propylene-based polymer degrading agent consisting of the diisopropylbenzene oligomer represented by the general formula (1) is used and heated to degrade the propylene-based polymer. By doing
Radical cleavage of the diisopropylbenzene oligomer. Then, the generated radicals abstract hydrogen atoms in the propylene-based polymer, and the generated radicals cause a self-cleavage reaction of the propylene-based polymer to be appropriately degraded.

According to the method for degrading a propylene-based polymer, since the degrading agent is a high molecular weight substance and is difficult to volatilize at the temperature during the degradation reaction, it can be effectively used as a propylene-based polymer degrading agent. Function. Therefore, it is possible to efficiently obtain a desired propylene polymer having a low odor.

[0034]

Next, Reference Examples, Examples and Comparative Examples will be given.
The present invention will be described more specifically. In addition, the part and% in each example show a weight part and weight% unless there is particular notice. Abbreviations in each example indicate the following compounds. PDIB-1: Diisopropylbenzene oligomer prepared in Reference Example 1 PDIB-2: Diisopropylbenzene oligomer prepared in Reference Example 2 PDIB-3: Diisopropylbenzene oligomer prepared in Reference Example 3 PDIB-4: Reference Example 4 Manufactured diisopropylbenzene oligomer BC: dicumyl DCP: dicumyl peroxide (Reference Example 1) m-methanol was placed in a 200 ml four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and an apparatus for distilling off low-boiling substances.
50 g of a mixture of diisopropylbenzene consisting of 59.4% of diisopropylbenzene and 40.6% of p-diisopropylbenzene were introduced. While stirring the mixture, 13
At 0 to 170 ° C, 90 g of di-t-butyl peroxide is added to 7
Dropped over time. The dropping was performed while distilling off low boiling components such as t-butanol, which is a decomposition product of di-t-butyl peroxide. Stirring was continued at the same temperature for 4 hours until the distillation of the low-boiling components was completed. After cooling,
42 g of a solid were obtained.

As a result of measuring the 1 H-NMR spectrum of this compound, signals of aromatic proton, methyl proton and methine proton derived from diisopropylbenzene unit were observed. Further, the number average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) is 920, and the obtained compound is diisopropylbenzene in which n in the general formula (1) is 5.7 on average. It was confirmed that it was an oligomer. (Reference Example 2) The addition amount of di-t-butyl peroxide was 7
The procedure was carried out in the same manner as in Reference Example 1 except that the amount was changed to 0 g. As a result, 40 g of a solid was obtained. As a result of measuring the 1H-NMR spectrum of this compound, signals of an aromatic proton, a methyl proton and a methine proton derived from a diisopropylbenzene unit were observed. Furthermore, the number average molecular weight in terms of polystyrene measured by GPC was 530, and it was confirmed that the obtained compound was a diisopropylbenzene oligomer in which n in the general formula (1) was 3.3 on average. . (Reference Example 3) The amount of di-t-butyl peroxide added was 1
The procedure was performed in the same manner as in Reference Example 1, except that the amount was changed to 20 g. As a result, 43 g of a solid was obtained. 1H-
As a result of measuring an NMR spectrum, signals of an aromatic proton, a methyl proton, and a methine proton derived from a diisopropylbenzene unit were observed. Further, the number average molecular weight in terms of polystyrene measured by GPC is 22.
10, and it was confirmed that the obtained compound was a diisopropylbenzene oligomer in which n in the general formula (1) was 13.8 on average. (Reference Example 4) The amount of di-t-butyl peroxide added was 1
The procedure was performed in the same manner as in Reference Example 1, except that the amount was changed to 50 g. As a result, 41 g of a solid was obtained. 1H-
As a result of measuring an NMR spectrum, signals of an aromatic proton, a methyl proton, and a methine proton derived from a diisopropylbenzene unit were observed. Further, the number average molecular weight in terms of polystyrene measured by GPC is 59.
70, and it was confirmed that the obtained compound was a diisopropylbenzene oligomer in which n in the general formula (1) was 37.3 on average. (Example 1) For 100 parts of polypropylene (trade name: Noblen H501, manufactured by Sumitomo Chemical Co., Ltd., MI value: 3.5),
0.05 parts of PDIB-1 produced in Reference Example 1 was mixed. It is fed to a kneading extruder, 240-250 ° C,
The mixture was kneaded with an average residence time of 5 minutes to produce pellets. The pellets were measured for MI value (230 ° C., 10 minutes, load 2.16 kg) and evaluated for odor. The results are shown in Table 1. The odor was evaluated according to the following criteria.

：: odorless or very faint odor
Δ: weak odor, ×: strong odor (Examples 2 to 8 and Comparative Examples 1 to 3) Performed according to Example 1, except that the type and amount of the reducing agent were changed as shown in Table 1. did. The results are shown in Table 1.

[0037]

[Table 1] As shown in Table 1, in Examples 1 to 8 using the diisopropylbenzene oligomer represented by the general formula (1) as a degenerating agent, dicumyl, a conventional carbon-carbon bond cleavage type radical generator, was used. As compared with Comparative Examples 1 and 2 used,
The obtained reduced propylene polymer is excellent in that it has no odor. Furthermore, comparison of the MI values of the degraded propylene-based polymers at the same addition amount shows that the diisopropylbenzene oligomers of Examples 1 to 8 have higher degradation efficiency than dicumyl. On the other hand, when dicumyl peroxide shown in Comparative Example 3 was used, although the degradation efficiency was high, the obtained reduced propylene polymer had a strong odor derived from the decomposition product.

The technical ideas grasped from the above embodiment will be described below. The method for degenerating a propylene-based polymer according to claim 2, wherein the heating is performed in a temperature range of 200 to 300 ° C.

In the case of such a constitution, the carbon-carbon bond of the diisopropylbenzene oligomer represented by the general formula (1) can be cleaved to effectively generate radicals, and the propylene polymer can be thermally decomposed. Thus, the degradation reaction of the propylene-based polymer can be effectively performed.

The propylene polymer degenerating agent according to claim 1, wherein the diisopropylbenzene oligomer represented by the general formula (1) is a meta-form or a para-form or a mixture of a meta-form and a para-form.

With such a constitution, the diisopropylbenzene oligomer represented by the general formula (1) can be easily obtained. The degradation for propylene-based polymer according to claim 1, wherein the diisopropylbenzene oligomer represented by the general formula (1) is obtained by oxidatively condensing diisopropylbenzene using a radical generator. Agent.

With this configuration, a diisopropylbenzene oligomer can be easily produced. A degrading method characterized by mixing a propylene-based polymer with a propylene-based polymer degrading agent comprising a diisopropylbenzene oligomer represented by the general formula (1) according to claim 1 and heating the mixture. A method for producing a propylene-based polymer.

According to this production method, by using the propylene polymer degrading agent according to claim 1, a propylene polymer which is appropriately degraded and has a low odor can be efficiently obtained. it can.

[0044]

As described in detail above, the present invention has the following excellent effects. According to the propylene polymer degenerating agent of the first invention, since it does not contain a peroxy bond, it is easy to handle, and it is difficult to volatilize, and a propylene polymer having little odor can be obtained.

According to the propylene polymer degrading method of the second invention, the propylene polymer degrading agent of the first invention is used to reduce the amount of propylene which is appropriately degraded and has a low odor. A system polymer can be obtained efficiently.

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Claims (2)

[Claims] 1. A propylene polymer degrading agent comprising a diisopropylbenzene oligomer represented by the following general formula (1). Embedded image (In the formula, n represents a number of 2 to 50.) 2. A propylene polymer degrading agent comprising a diisopropylbenzene oligomer represented by the general formula (1) according to claim 1 is mixed with the propylene polymer,
A method for degrading a propylene-based polymer, comprising heating.