JPS6322210B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a graft modified product. More specifically, the present invention relates to a method for producing a graft-modified product by graft-modifying a thermoplastic resin using a screw extruder. BACKGROUND ART In order to impart functionality such as adhesiveness, compatibility, and reactivity to thermoplastic resins such as polyolefins, it is widely practiced to modify them by grafting various monomers or oligomers onto them.
Graft modified products have the characteristic of being able to add new desired properties without substantially impairing the properties of the base resin, so they are useful in many fields, including adhesive resins. It is served to. Graft modification methods include introducing active sites such as free radicals into the resin and bringing them into contact with monomers or oligomers that react with and bond with the radicals, or to resins with functional groups.
There are methods such as contacting monomers or oligomers that react with the functional group to be bonded, and specifically, the graft modified product is produced by the following method. (1) A method in which the base resin is dissolved in an organic or inorganic solvent and reacted in that solution. In the case of this method, the process of separating the resin and solvent after the reaction, washing, purifying, and drying the resin is inevitably involved, so that the modified resin has less coloring and odor, and the modified resin has less color and odor. Although it has the advantage of containing low molecular weight substances such as unreacted monomers, it requires a large number of steps and requires a relatively large amount of energy to purify the solvent used and dry the modified resin.
The disadvantage is that it is not economical. (2) A method in which the surface of a solid resin is irradiated with radiation such as an electron beam to provide active sites, and then a gaseous or liquid monomer is brought into contact with the surface. This method is a reaction only on the surface of the solid resin, and is limited to surface modification of resin molded products of specific shapes such as films, and requires special equipment such as radiation irradiation equipment, and is inefficient. , the disadvantage is that the modification cost is high. (3) A method in which monomers or oligomers are introduced into a molten resin and reacted using a resin melt processing device such as a screw extruder. This method uses fewer substances that are not directly involved in the reaction, such as solvents, uses only a resin kneading device, has fewer steps, and has a high reaction rate.
It is the most economical method and is commonly used because it is easy to perform as a continuous process. However, in the case of this method, unreacted monomers and low molecular weight by-products are contained in the modified resin as they are.
Depending on the type, there may be a noticeable odor or pungent odor. In particular, unsaturated carboxylic acids or their esters such as maleic anhydride and acrylic acid, vinyl esters such as vinyl acetate, unsaturated hydrocarbons such as styrene, and unsaturated silane compounds such as trimethoxyvinylsilane are extensively graft-modified. However, its odor is also noticeable. In order to solve the problem of odor observed in graft modified products produced by the melting method, a method is known in which unreacted monomers are extracted and removed from modified resin pellets or pulverized powder using a solvent. The additional steps of recovery, purification and drying of the modified product greatly reduce the economic advantage of this process. Another method is to send heated air or nitrogen gas to the modified resin pellets to purge unreacted monomers, but in this case, the removal efficiency is poor unless the unreacted monomers have a low boiling point, and in addition, they are odor-prone. It will also be necessary to treat gases containing components. Furthermore, there is a known method in which volatile components are degassed under reduced pressure through a vent provided in the middle of the extruder during the production of graft modified products; However, monomers that are solid at room temperature, such as maleic anhydride, and high-boiling monomers, such as acrylic acid and vinyl silane, cannot sufficiently remove them. It is an object of the present invention to eliminate unreacted monomers and other low molecular weight substances contained in the modified resin without losing the advantageous economic characteristics of this production method when producing a graft modified resin using a screw extruder. The objective is to effectively remove odorous components. Therefore, the present invention relates to a method for producing a graft modified product, and in this production method, when producing a graft modified product of a thermoplastic resin using a screw extruder, a single screw extruder is used, and the extruder is Approximately 10 kg of water that does not directly participate in the reaction, or liquid hydrocarbons with a boiling point of 150°C or less, or their oxygen-containing compounds are added through an injection port provided in the middle.
By injecting and dispersing under a pressure of at least cm ² and then removing the injected liquid and low molecular weight substances from a vent port provided downstream of the injection port of the extruder under an absolute pressure of 400 mmHg or less. A graft modification is produced. In the present invention, a screw extruder called a vent (deaeration) extruder is used, and there are two types, one with a single screw and the other with a double screw.The one with a single screw is used from the viewpoint of degassing efficiency and economy. It will be done. This extruder is usually divided into seven zones.
That is, from the upstream side, there is a supply section with a base resin supply port, a compression section that melts the resin, a first metering section that adjusts the resin flow rate, a mixing section where resin mixing and grafting reaction are mainly performed, and a pressure control section in the mixing section. hold,
The aperture ring part has the function of improving reaction and deaeration efficiency in the downstream deaeration part, the deaeration (vent) part for deaeration, and the second part for extruding the molten resin.
Consists of a measuring section. The first measuring section can also serve as a mixing section.
The aperture ring also has the purpose of maintaining the pressure at the injection point of the injected liquid, but the shape does not need to be ring-shaped as long as it has the function of maintaining pressure. The deaeration section has a vent port for deaeration, which is connected to an evacuation device such as a vacuum pump or ejector through piping. An exhaust gas cooling and separation device is installed between the exhaust device and the vent port, and the injected liquid is separated and recovered. One or more injection ports for injecting the liquid used in the present invention are provided between the compression section and the mixing section, and the liquid sent from the pump is injected into the resin in the extruder from this injection port. Ru. Production of a graft modified product using such a single screw extruder is usually carried out as follows. To the feed section of the extruder, thermoplastic resin pellets,
Supply powder etc. However, in cases such as an extruder installed after the thermoplastic resin polymerization process, the resin can also be supplied in a molten state. In addition to the thermoplastic resin, the supply section is supplied with a graft modification catalyst, a polymerization initiator, a solid monomer, an oligomer, and the like. The injection liquid is pumped using a pump to a pressure higher than the internal pressure of the extruder at the injection position, approximately 10
Injected under pressure of Kg/cm2 or ^more . Components involved in the reaction, such as monomers, oligomers, graft modification catalysts, polymerization initiators, etc., either in liquid form or dissolved or dispersed in a suitable solvent, are also mixed with the injection liquid or pumped into the extruder from a separate line. The graft modification reaction is carried out mainly in a zone where reaction components such as the base resin, monomers, or oligomers coexist and the resin satisfies the conditions for maintaining a molten state, that is, between the compression section and the mixing section, mainly in the mixing section. In order to carry out the reaction uniformly and quickly, it is preferable to maintain the reaction under pressure. Also,
This pressure is applied to increase the efficiency of the injected liquid being dispersed in the resin, and then when this pressure is released in the degassing section, the liquid bubbles and vaporizes from inside the resin, removing components such as unreacted monomers. is also necessary. For this reason, this pressure needs to be about 10 kg/cm ² or more, and the transport speed of the molten resin by the rotation of the screw from the upstream side of the first supply section and the aperture ring installed next to the mixing section This pressure is regulated and maintained by the action of transport-limiting mechanisms such as . Single-screw extruders are preferred because this pressure retention is achieved with a simple mechanism such as a squeeze ring, whereas twin-screw extruders require
Generally, it is difficult to maintain such pressure, and a complicated mechanism is required to maintain the pressure. The temperature of this reaction zone is generally about 100-300℃
is kept within the range of The reaction mixture is transported from the reaction zone through the aperture ring section to the degassing section. Since this zone is maintained under reduced pressure by an exhaust device such as a vacuum pump, the resin is degassed while foaming due to vaporization and expansion of the liquid contained inside the resin. At this time, unreacted monomers and the like are removed along with the degassed gas. The degassed gas is exhausted through piping leading to the exhaust device, liquefied or solidified and separated by a cooling separation device provided in the middle of the piping, and recovered. The pressure in the degassing section is absolute pressure from the viewpoint of degassing effectiveness.
Maintained at 400 mmHg or less, preferably 200-20 mmHg. The degassed graft modified product is processed again in the second supply section, extruded out of the extruder, and cut into pellets or the like. Thermoplastic resins to be subjected to graft modification include resins molded using a screw extruder, such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, polyamide, polyester, Examples include polybutadiene, but polyolefins and ethylene copolymers are particularly preferred. As the compound grafted onto these thermoplastic resins, unsaturated monomers or oligomers that are liquid or solid at room temperature are preferably used. Monomers that are gaseous at room temperature can also be used, but in this case the effect of liquid injection is less. Suitable grafting monomers include ethylenically unsaturated carboxylic acids or their anhydrides such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, ethylenically unsaturated carboxylic acid esters such as ethyl acrylate, methyl methacrylate, etc. , vinyl esters such as vinyl acetate, ethylenically unsaturated hydrocarbons such as styrene, and vinyl silanes such as vinyltrimethoxysilane. Among these, the method of the present invention is effectively applied to substances that have a high boiling point and cannot be removed from the resin by a simple degassing operation, such as ethylenically unsaturated substances such as maleic anhydride and acrylic acid. This includes carboxylic acids and vinylsilanes such as vinyltrimethoxysilane.
Furthermore, when the trunk polymer (base resin) has a carboxylic acid group or a carboxylic acid anhydride group, caprolactam or the like which is reactive with these functional groups can also be used. The liquid injected at the intermediate position of the extruder is:
Water, a liquid hydrocarbon with a boiling point of 150° C. or lower, or an oxygen-containing compound thereof is used. Examples of hydrocarbons used include n-hexane, toluene, and xylene, and examples of their acid-containing compounds include alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, ethers such as dioxane, and ethyl acetate. Ester etc. are used. If a liquid having a boiling point higher than 150° C. is used, degassing from the resin in the degassing section of the extruder becomes insufficient and the removal efficiency of unreacted monomers etc. decreases, which is not preferable. Further, the injection liquid needs to be injected in liquid form. If injected in gaseous form, it will not be sufficiently dissolved in the resin in the extruder,
It becomes easier to phase separate from the molten resin in the reaction zone,
The injected liquid foams from inside the resin in the degassing section, and the entrainment effect of unreacted monomers and the like when degassing is reduced. One or more types of injection liquid are appropriately selected depending on the types of base resin, graft monomer, and polymerization initiator and reaction conditions. When two or more types of liquids are used, for example, when they are used in an azeotropic system such as xylene-water, the removal efficiency of unreacted monomers etc. may be significantly improved. Also,
The injection liquid can be injected from one or more locations separately or in a mixture with the graft monomer and polymerization initiator. The amount of injection is generally about 2 to 20% by weight, preferably about 3 to 15% by weight based on the base resin; if it is less than this, the removal efficiency of unreacted monomers etc. is low, while if it is used more than this, It becomes difficult to operate the extruder. As mentioned above, it has been known to produce graft modified products using a vent extruder;
In the method of the present invention, by injecting a liquid other than the monomer into the intermediate position of the single screw extruder,
The removal efficiency of residual unreacted monomers, etc. in the degassing section is greatly increased. This effect is caused by the injected liquid being dissolved into the resin by pressure in the zone upstream of the degassing section, and then vaporized from inside the resin when released by the pressure in the degassing section, resulting in foaming. This is thought to be obtained because unreacted monomers and the like are effectively entrained during degassing. Therefore, it is necessary that the liquid be injected into the extruder in a liquid state, and that the injection amount be sufficient to entrain unreacted monomers and the like. This effect is most effectively exhibited in the case of graft modification using a graft monomer such as maleic anhydride, which has a high boiling point and is difficult to remove by mere degassing in an extruder. In addition, when using a graft monomer that is corrosive to metals, such as acrylic acid, the degree of corrosivity is reduced by diluting it with liquid injection, which may cause damage to the equipment or discoloration of the grafted modified product. When the amount decreases, the effect of Itsuta can also be obtained. As a result of effectively removing residual unreacted monomers and other low molecular weight substances, the odor and sanitary properties of the graft modified product caused by these substances are significantly improved. In addition, from an operational standpoint, since unreacted monomers and the like can be removed in a closed system, no odor is released to the outside during production, which greatly improves the working environment and air pollution problems. Furthermore, it is possible to omit the conventional processes such as solvent extraction and hot air drying that were required to remove unreacted monomers, and the energy and equipment required for this process are also eliminated. . Next, the present invention will be explained with reference to examples. Examples 1 to 4 100 parts of ethylene polymer pellets (weight, same hereinafter), 2,5-
A dry blend of 0.05 part of dimethyl-2,5-bis(tert-butylperoxy)hexyne-3 polymerization initiator and 1.0 part of maleic anhydride powder was added every hour.
Graft modification was carried out by supplying at an amount of 2.0 kg. The extruder used is divided into a supply section, a compression section, a first measuring section, a mixing section, a squeeze ring, a degassing section, and a second measuring section from the supply port toward the die side. The compression section and the first metering section are each provided with a single injection port for liquid, each of which is connected to an injection pump. The vent port is provided in the degassing section and is connected to the vacuum pump by piping through the cooling trap. The temperature of the extruder was maintained at 250°C between the first measuring section and the mixing section, and at 180°C in the degassing section. Furthermore, the pressure in the degassing section is
A vacuum of 60-140 mmHg absolute was maintained. In the graft modification operation, first, 5% by weight of n-hexane or xylene based on the base resin was injected with a pump from the injection port of the first measuring section under a pressure of 10 kg/cm ² or more. The injected liquid was recovered in a cooling trap cooled with ice water with a recovery rate of over 85% by degassing from the vent port on the downstream side. The grafted modified product is continuously extruded in the form of a strand from the die at the tip of the extruder, and is cooled in water.
It was cut into pellets using a cutter. The strands and pellets were colorless and transparent, and no odor of maleic anhydride was detected. The obtained pellets were refluxed with methanol for 3 hours using a Soxhlet extractor to extract unreacted graft monomers. When the amount of maleic anhydride grafted in the graft modified product after extraction and the amount of unreacted maleic anhydride in the extract were analyzed by alkaline titration, it was found that most of the unreacted maleic anhydride was removed in the extruder. It was found that the graft modified product extruded from the extruder contained only a very small amount of unreacted graft monomer. Comparative Examples 1-2 In Examples 1-3, no liquid was injected. The strands and pellets of the grafted modified product extruded from the extruder have a pungent odor, and the results of a similar analysis of the amount of maleic anhydride grafted and the amount of unreacted maleic anhydride indicate that the unreacted graft monomer in the extruder The removal efficiency of
It was found that a large amount of unreacted maleic anhydride remained in the obtained graft modified product. Furthermore, if the graft modification operation is carried out for a long time, maleic anhydride crystals will clog the exhaust pipe to the vacuum pump, making it impossible to continue operation. The results of each of the above Examples and Comparative Examples are summarized in Table 1 below.

[Table] Examples 5 to 7 Ethylene-vinyl acetate copolymer (MI30,
A blend of 100 parts of (vinyl acetate content: 33% by weight) pellets and 0.2 parts of liquid tert-butylperoxy-2-methylhexanoate polymerization initiator was fed at a rate of 2.0 kg/hour to carry out graft modification. Summer. The temperature of the extruder is 200℃ from the first measuring section to the mixing section.
Alternatively, the degassing section was maintained at 170°C. Maleic anhydride is dissolved in various liquids at a predetermined ratio to the resin, and placed in the compression section of an extruder at a ratio of 2% by weight of maleic anhydride to the base resin under a pressure of 10 kg/cm ² or more. I injected it with a pump. In addition, the degassing section was maintained at an absolute pressure of 60 mmHg. The strands and pellets of the grafted modified product extruded from the extruder had almost no odor. In addition, from the analysis results of the amount of maleic anhydride grafted and the amount of unreacted maleic anhydride, it was found that most of the unreacted maleic anhydride was removed in the extruder, and the graft modified product extruded from the extruder contained It was found that only a small amount of maleic anhydride remained. Comparative Example 3 Similar operations were carried out as in Examples 5-7, except that the maleic anhydride was pre-dry blended as a powder with the base resin pellets and fed to the extruder and no liquid injection was performed. The strands and pellets of the grafted modified product extruded from the extruder had a significant odor, and a considerable odor was also felt around the extruder. The graft modified product is colored yellow, and the analysis results of the amount of maleic anhydride grafted and the amount of unreacted maleic anhydride indicate that the content of unreacted monomer in the graft modified product is high, and it must be removed in the extruder. It was found that the efficiency was low. The results for Examples 5-7 and Comparative Example 3 are summarized in Table 2 below.

[Table] Acetone (3)
〃 6 Toluene (7)／ 10.0 6
0 8.1 0.78 0.084
Acetone(3)

〃 7 Acetone 5.0 8
0 6.8 0.71 0.150
Comparative example 3 − − (1
15) 7.8 0.89 0.821
Examples 8 to 10 Into the single screw vent extruder used in Example 1, 100 parts of ethylene copolymer pellets and 0.1 part of liquid tert-butylperoxy-2-ethylhexanoate polymerization initiator (however, In Example 10, 0.2 parts) of the blend was fed at a feed rate of 2.0 Kg/hour. The temperature conditions of the extruder were set to the same conditions as in Examples 5-7. A predetermined amount of acrylic acid is diluted 5 times with a mixed solution of xylene (1)/n-hexane (3) based on the resin, and pumped into the compression section of the extruder under a pressure of 10 kg/cm ² or more. did. In addition, the degassing section was maintained at an absolute pressure of 60 mmHg. The strands and pellets of the grafted modified product extruded from the extruder had almost no odor. Further, from the analysis results of the amount of acrylic acid grafted and the amount of unreacted acrylic acid for this uncolored graft modified product, it was found that most of the unreacted graft monomer was removed in the extruder. Comparative Example 4 In Example 8, acrylic acid was not diluted with the mixed solution and the amount of polymerization initiator was changed to 0.2 parts,
Graft modification was performed. The strands and pellets of the grafted modified product extruded from the extruder had a considerable odor, and the odor was also felt around the extruder. The results of Examples 8-10 and Comparative Example 4 are summarized in Table 3 below.

[Table] Example 11 Ethylene-vinyl acetate copolymer (MI70,
A blend of 100 parts (vinyl acetate content 45% by weight) and 0.2 parts of liquid tert-butylperoxy-2-ethylhexanoate polymerization initiator was fed at a feed rate of 2.0 kg/hour. The temperature of the extruder is 200℃ from the first measuring section to the mixing section.
Additionally, the degassing section was maintained at 180°C. Trimethoxysilane was used at a ratio of 2.2 parts per 100 parts of base resin, and this was mixed with twice the amount of xylene(1)/n-hexane.
(3) Dilute with mixed solution and add 50Kg/
Pumped under pressure of cm ² . In addition, the pressure in the degassing section was maintained at 60 mmHg in absolute terms. The graft modified strands and pellets extruded from the extruder had almost no odor. The amount of trimethoxysilane grafted in this graft modified product was measured to be 1.1% by weight, and the amount of unreacted monomer was 0.07% by weight. Example 12 Ethylene-vinyl acetate copolymer (MI9.5,
A blend of vinyl acetate (vinyl acetate content 10% by weight) and 0.1 part of liquid tert-butylperoxy-2-ethylhexanoate polymerization initiator was fed at a feed rate of 2.0 kg/hour. The temperature of the extruder is 200℃ from the first measuring section to the mixing section.
Additionally, the degassing section was maintained at 180°C. Acrylic acid was used at a rate of 2.0 parts per 100 parts of base resin and was pumped into the compression section of the extruder. Also,
5% by weight of water based on the base resin was injected into the first metering section with a pump at a pressure of 100 kg/cm ² . The pressure in the degassing section was maintained at 60 mmHg in absolute terms. The graft modified product strands and pellets extruded with an extruder had almost no odor. When the amount of acrylic acid grafted in this graft modified product was measured, it was 1.1% by weight, and the amount of unreacted monomer was 0.05% by weight. Comparative Example 5 The dry blends of Examples 2 and 3 were fed at a rate of 2.0 kg per hour into a co-rotating twin-screw vent extruder with a diameter of 30 mm (L/D = 25) and one vent port. Supplied in quantity. This extruder is equipped with a seal ring (having the function of a squeeze ring) upstream of a degassing section, and a kneading disk (kneading section) further upstream of the seal ring. The temperature of the extruder is set at the kneading disc section.
The temperature was maintained at 250°C and at 180°C in the degassing section. The pressure in the degassing section was maintained at a reduced pressure of 60 mmHg in absolute terms.
During graft modification, 5% by weight of xylene with respect to the base resin is injected with a pump just before the kneading disk, and the pressure of the injected liquid during modification is 5 Kg/
held at ^cm2 . The obtained graft modified product had a considerable odor, and the amount of grafted maleic anhydride was 0.51% by weight, and the amount of unreacted maleic anhydride was 0.20% by weight. Comparative Example 6 In Example 3, a vent extruder was used in which the clearance of the squeeze ring portion of the screw was widened. During operation of the extruder, the extruder internal pressure at the inlet pulsated within the range of 0 to 7 Kg/ ^cm2 . Along with such pressure pulsations, the flow of resin and liquid entering the degassing section fluctuated, and the degassing state such as vaporization of the injected liquid in the degassing section varied. The obtained graft modified product had an odor, and the amount of grafted maleic anhydride was 0.23% by weight, and the amount of unreacted maleic anhydride was 0.22% by weight.

Claims (1)

[Scope of Claims] 1. When producing a graft modified thermoplastic resin using a screw extruder, a single-screw extruder is used, and an injection port provided in the middle of the extruder is used to produce a graft-modified product that does not directly participate in the reaction. water or boiling point
A liquid hydrocarbon or its oxygen-containing compound at a temperature of 150°C or less is injected and dispersed under a pressure of about 10 kg/cm ² or more, and then the absolute pressure is A method for producing a graft modified product, characterized by removing an injected liquid and a low molecular weight substance under a pressure of 400 mmHg or less. 2. The method for producing a graft modified product according to claim 1, wherein about 2 to 20% by weight of liquid is injected based on the thermoplastic resin.