JPS6229442B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a graft polymer of powdery polyolefin. In order to improve the physical properties of polyolefins, attempts have been made to graft a different type of polymer having a structure different from that of the base polymer of the polyolefin onto the base polymer. As graft polymerization methods, for example, suspension graft polymerization in a liquid phase or solution graft polymerization method are known, but these methods require heating of the liquid medium, filtration after polymerization, and drying steps, and many process steps are required. It requires a lot of energy and is complicated. Also known is a method of graft polymerization by heating and melting a polyolefin in which a radical initiator and a solid or liquid monomer are uniformly mixed. Although it is possible to achieve a relatively high grafting rate with this method, it has drawbacks such as the inability to obtain uniform grafting due to generally poor compatibility between polyolefin and monomer, and accelerated thermal degradation of polyolefin. There is. Furthermore, since the polyolefin is melted, a large amount of energy is consumed and it is not suitable for large-scale processing. Furthermore, a method of graft polymerizing a monomer onto a base polymer in the gas phase is also known, but the previous methods either require irradiation with radiation to generate radicals on the base polymer before graft polymerization, or The base polymer is suspended in a liquid medium, an initiator is added and heated to retain hydroperoxide groups on the base polymer. Therefore, any gas phase graft polymerization method requires a two-step operation: generation of a polymerization initiation site followed by graft polymerization. As a result of repeated research into methods for graft polymerizing various monomers onto polyolefin base polymers, the present inventors have discovered that a method for graft polymerizing various monomers onto a polyolefin base polymer has been found to be easy and favorable by bringing a liquid radical initiator into contact with a powdery polyolefin and then grafting it in a vapor phase. It was discovered that a modified graft polymer of polyolefin can be obtained,
The invention has been completed. That is, in the present invention, a powdery polyolefin is uniformly brought into contact with a liquid radical initiator, and then a gaseous radically polymerizable material is heated at a temperature lower than the melting temperature of the powdery polyolefin and higher than the decomposition temperature of the radical initiator. A method for producing a modified polyolefin, which comprises bringing it into contact with a monomer and graft polymerizing it in a gas phase. It is. The present invention is an energy-saving process because it is a dry process that does not use a liquid medium and does not require a filtration and drying step after the reaction. Furthermore, since the monomers are graft-polymerized in the coexistence of a base polymer and a liquid initiator, it is a very simple one-step process, which is extremely advantageous in terms of industrial production. Furthermore, the grafting efficiency is much better than that of liquid phase graft polymerization, and the grafted polymer is not simply grafted onto the surface of the polyolefin polymer, but is evenly and finely dispersed inside the olefin polymer. . Figures 1 and 2 are a scanning electron micrograph and an X-ray microanalyzer chlorine analysis photograph of a fractured cross section of unmodified polypropylene particles, respectively. Figure 3,
FIG. 4 is a scanning electron micrograph and an X-ray microanalyzer chlorine analysis photograph of a fractured cross section of modified polypropylene particles grafted with polyvinyl chloride obtained according to an example of the present invention. Each white dot in Figure 4 represents the presence of chlorine, and by comparing Figures 2 and 4, it can be seen that the grafted polyvinyl chloride is evenly dispersed inside the polypropylene. The olefin polymer used in the present invention is an olefin homopolymer or copolymer represented by the general formula CH ₂ ═CH—R (R is hydrogen, an alkyl group, or an alkenyl group). It is usually preferable to use a homopolymer of ethylene or propylene or a copolymer of propylene and ethylene. Therefore, in the present invention, it is essential to use a powdery polyolefin in order to be able to uniformly contact the liquid radical initiator and to successfully achieve graft polymerization in the gas phase. Such powdery polyolefins generally have an average particle diameter of 0.01 to 3 mm, particularly preferably 0.05 to 2 mm. In addition, in the present invention, in order to easily and efficiently graft a radically polymerizable monomer onto the powdery polyolefin in the gas phase, and thereby obtain a good modified polyolefin, a liquid radical initiator is applied to the powdery polyolefin in advance. Uniform contact is extremely important. That is, according to the present invention, it is possible to obtain a modified polyolefin in which the graft polymer is finely dispersed into the interior of the polyolefin with high grafting efficiency. As mentioned above, although the mechanism of action by which modified polyolefin can be obtained satisfactorily in the present invention cannot be clarified, in particular, by uniformly contacting the powdery polyolefin with a liquid radical initiator in advance, the polyolefin powdery and granular It is presumed that since the radical initiator penetrates into the interior, graft polymerization is then effectively achieved. The radical initiator used in the present invention is not particularly limited as long as it is liquid. For example, hydroperoxides (t-butyl hydroperoxide, cumene hydroperoxide, etc.),
Dialkyl peroxides (di-t-butyl peroxide, t-butylcumyl peroxide, etc.), ketone peroxides (methyl ethyl ketone peroxide, cyclohexane peroxide, etc.), peroxy esters (t-butyl peroxyacetate, t-butyl peroxide, etc.) -Butylperoxyisobutyrate, t-butylperoxypiparate, t-butylperoxyoctanate, t-butylperoxybenzonate, t-butylperoxylaurate, t-butylperoxyneodecanate, t -butyl peroxyisopropyl carbonate, etc.), diacyl peroxides (isobutyryl peroxide, octanoyl peroxide, acetyl peroxide, etc.), peroxycarbonates (Gi-isopropyl peroxydicarbonate, Di-2-ethylhexyl peroxide, etc.) Peroxides such as oxydicarbonate, Di-n-propyl peroxydicarbonate, Di-sec-butyl peroxydicarbonate, etc.) can be used. Particularly preferred is a peroxide having a relatively low boiling point, which has a low decomposition temperature and whose vapor easily penetrates into the interior of the polyolefin. In other words, the decomposition temperature is 100℃ or less, and the boiling point is 150℃/1mmH.
g peroxides such as t-butylperoxypivalate, t-butylperoxyisobutyrate, t-butylperoxyoctanate, t-butylperoxyneodecanate, di-isopropylperoxydicarbonate, Di-2-ethylhexyl peroxydicarbonate, acetyl peroxide, isobutyryl peroxide, and octanoyl peroxide are good. These initiators may be mixed with a small amount of liquid hydrocarbons such as aliphatic hydrocarbons and aromatic hydrocarbons, if necessary.
Alternatively, it may be brought into contact with powdery polyolefin in combination with a plasticizer such as dimethyl phthalate. The method of uniformly bringing the liquid radical initiator into contact with the powdery polyolefin is not particularly limited. The granular polyolefin and the liquid radical initiator may be thoroughly mixed using a generally known mixing means at room temperature to a temperature below the temperature at which the radical initiator begins to decompose. It is also advisable to sufficiently stir and mix both in the polymerization vessel in which the graft polymerization reaction is carried out. The amount of radical initiator used is usually 100g of polyolefin.
0.1 to 30 mmol, particularly 0.5 to 10 mmol is preferable. Next, in the present invention, a monomer capable of radical polymerization is introduced into the polymerization system, and graft polymerization is performed in the gas phase.
The polymerization method is not particularly limited, and may be a batch method or a continuous method, and stirring can be carried out mechanically or in a fluidized bed method. The polymerization temperature may be any temperature at which the liquid radical initiator decomposes and the reaction begins. However, at low temperatures, the reaction rate of gas phase graft polymerization is slow, which is disadvantageous in terms of production.If the temperature is too high, the base polymer polyolefin decomposes, so the temperature is usually 20 to 150℃, preferably 30 to 100℃.
Do it with The polymerization pressure must be such that the graft monomer is polymerized in the gas phase and does not liquefy at that temperature. The polymerization time is arbitrarily determined depending on the amount of grafting. Incidentally, the graft polymerization reaction is usually carried out under an atmosphere of an inert gas such as nitrogen or argon. The radically polymerizable monomers used in the present invention include vinyl chloride, vinyl acetate, vinylpyridine, styrene, acrylonitrile,
Examples include (meth)acrylic acid and (meth)acrylic ester, and vinyl chloride is preferably used, but is not particularly limited to these. The modified olefin polymer obtained in the present invention has superior physical properties compared to unmodified olefin polymer. Conventionally, homogeneous mixing and molding of polyolefin and polyvinyl chloride, for example, has been difficult due to phase separation, but by using this modified olefin polymer, it is easy to obtain a uniformly mixed molded product of polyolefin and polyvinyl chloride. I can do it. For example, simply blending dioctyl phthalate, polyvinyl chloride, and polypropylene will cause phase separation and result in a cloudy, nonuniform thermoplastic elastomer, but if a modified olefin polymer is used, it will be uniformly transparent, oil resistant, A thermoplastic elastomer with excellent flame retardancy can be obtained. Furthermore, compared to a simple blend of olefin polymer and polyvinyl chloride, this modified olefin polymer grafted with polyvinyl chloride is superior in particular in terms of tensile strength and impact strength. Examples of the present invention will be described below, but the present invention is not limited thereto. In addition, data and evaluation in Examples and Comparative Examples were performed by the following method. (a) Measurement of the polyvinyl chloride content in the modified olefin polymer The amount of chlorine atoms in the polymer is determined by a conventional elemental analysis method, and the value is used to determine the polyvinyl chloride content in the modified olefin polymer. Count backwards. (b) Measurement of grafting efficiency A predetermined amount (approximately 1 g) of modified olefin polymer was placed in a cylindrical filter paper in a Soxhlet extractor, and tetrahydrofuran (hereinafter abbreviated as THF) was added as a solvent at 100%
ml and heated under reflux for 7 hours to separate into THF-soluble homopolyvinyl chloride and THF-insoluble vinyl chloride grafted polyolefin. After drying the THF-insoluble part under reduced pressure, polyvinyl chloride was prepared by method (a). The content of is determined, and the grafting efficiency is calculated using the following formula. Grafting efficiency = Content of polyvinyl chloride in THF-insoluble portion / Content of polyvinyl chloride in unextracted modified olefin polymer x 100% (c) Measurement of tensile strength and impact strength 3.5-jeta shear for 20 g of polymer Add 1 phr of l-butyl-1,4-hydroxytoluene and 3 phr of dibutyltin malate, mix evenly, and then hot press at 160°C to make a press sheet. This press sheet was cut out, placed in a mold for measuring physical properties, heated at 180°C for 10 minutes, and then heated for 3 minutes.
Cool press at 50Kg/cm ² to make a measurement sheet.
Cut out measuring dumbbells from this sheet and use them for 24 hours.
After aging at 23°C, physical properties were measured. Example 1 After purging the pressure-resistant glass autoclave No. 1 equipped with a stirring device with a helical double ribbon with argon gas, 80 g of powdery crystalline polypropylene and 4 mM of tert-butyl peroxypivalate (hereinafter abbreviated as LII) were added. Add and stir for 4 minutes. After this, the pressure of the system was reduced for 1 minute, and then vinyl chloride monomer was introduced at 60°C. Reaction pressure 5.0Kg/cm ²
Then, the vinyl chloride monomer was continuously supplied while maintaining the reaction temperature at 60℃, and the graft polymerization reaction was allowed to proceed for 4 hours while stirring. After the polymerization was completed, the system was purged and 134 g of white powder-like modified polypropylene was obtained. I got it. After removing homopolyvinyl chloride from this polymer by THF extraction, the content of polyvinyl chloride, grafting efficiency, and mechanical properties were measured. Example 2 Tert-butyl peroxyoctanate was used instead of 4mM of the liquid radical initiator LII in Example 1.
The same procedure as in Example 1 was performed except that 1 mM was used. Example 3 The same procedure as in Example 1 was carried out except that the reaction time in Example 1 was extended from 4 hours to 7 hours and the amount of polyvinyl chloride grafted was increased. Example 4 The same procedure as in Example 1 was carried out except that 300 g of granular polyethylene was used instead of the granular crystalline polypropylene of Example 1 and the reaction was carried out for 1 hour. Comparative Example 1 In Examples 1 to 4, no liquid reaction medium was used, but in order to clarify the difference from the gas phase graft reaction, 400 ml of heptane and tert-butylperoxyisobutyrate (hereinafter referred to as
Graft polymerization was carried out in a liquid using BPIB (abbreviated as BPIB). Other than that, the same procedure as in Example 1 was carried out. Comparative Example 2 300ml of xylene instead of heptane in Comparative Example 1
The same procedure as Comparative Example 1 was carried out except that . Comparative example 3 Crystalline polypropylene 80 phr and polyvinyl chloride
The physical properties were measured using a polymer blended with 20phr. Comparative example 4 Crystalline polypropylene 70phr and polyvinyl chloride
Comparative Example 3 was carried out in the same manner as in Comparative Example 3 except that a polymer blended with 30 phr was used. This corresponds to Example 3. The results of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1.

【table】

[Table] Example 5 Using the same polymerization apparatus as in Example 1, 130 g of powdery crystalline polypropylene and 2.85 mM of BPIB were charged, stirred for 4 minutes, 18 g of styrene was added, and grafted for 1 hour while maintaining the reaction temperature at 80°C. When the polymerization reaction proceeded, 145 g of white powdery modified polypropylene was obtained. This polymer was extracted with benzene, the insoluble portion was filtered and dried, and the content of grafted polystyrene was measured to be 9.8.
It was %. In addition, the grafting efficiency was 85%.

[Brief explanation of the drawing]

Figures 1 and 2 are a scanning electron micrograph (200x magnification) and an X-ray microanalyzer chlorine analysis photograph (200x magnification) of a fractured cross section of the unmodified polypropylene particles used in Example 1, respectively. 3 and 4 are a scanning electron micrograph and an X-ray microanalyzer chlorine analysis photograph of the modified polypropylene obtained in Example 1, respectively.

Claims (1)

[Claims] 1. After uniformly contacting a powdery polyolefin with a liquid radical initiator, gaseous radicals are heated at a temperature lower than the melting temperature of the powdery polyolefin and higher than the decomposition temperature of the radical initiator. A method for producing a modified polyolefin, which comprises bringing it into contact with a polymerizable monomer and carrying out graft polymerization in a gas phase. 2. The method according to claim 1, wherein the radically polymerizable monomer is a vinyl chloride monomer. 3 As a liquid radical initiator, the decomposition temperature is 100℃
Hereinafter, the method according to claim 1, in which a peroxide having a boiling point of 150° C./1 mmHg or less is used.