Abstract:
This invention relates to a method for graft-copolymerizing vinyl chloride monomer to a polyfluorine resin to produce resins of improved physical properties and processability parameters. The vinyl chloride monomer and polyfluorine resin are first treated in a highly alkaline medium and at a high temperature, and the mixture is stirred. Suspension agent(s), water and an initiator are added to the mixture after the temperature thereof has been lowered. The resultant mixture which has been stirred and homogenized is heated to a temperature at which polymerization is completed. Thereafter the mixture is neutralized, washed, and dried. A product having improved impact strength and resistance to heat and abrasion results.

Description:
BACKGROUND OF THE INVENTION 
     Polyvinyl chloride resin is used extensively in daily life; however, it presents many disadvantages including being relatively weak in impact strength, and having low resistance to heat and to abrasion. Polyfluorine resin, on the other hand, possesses better physical properties relative to polyvinyl chloride. Based on the observation of improved physical properties of the polyvinyl chloride when grafted with polyfluorine resin, the search has continued for a new method of graft-polymerization to produce a new material having superior physical properties. The drawbacks in the polyvinyl chloride are thus eliminated. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to develop a method for producing a material having characteristics of both polyvinyl chloride and polyfluorine resin, which is advantageous in being inexpensive to produce. Polyfluorine resin has superior processing properties; however, because of its high cost it has not been used widely. Further, this resin requires high temperature in processing, and flowability is not satisfactory. Therefore, there are many restrictions in processing of the resin. In contrast, products prepared by graft-polymerization of polyfluorine resin and vinyl chloride monomer not only possess the advantages of polyvinyl chloride, e.g., low in cost, but are, like polyfluorine resin, better in processing flowability, low in viscosity and readily processable. In addition, these specific materials possess high impact strength and resistance to chemicals, abrasion, wear, and heat, so that resorces can be used economically. 
     DETAILED DESCRIPTION 
     The present invention relates to a process for graft-copolymerization of vinyl chloride and polyfluorine resin and to the copolymers produced thereby. Accordingly, vinyl a mixture of chloride monomer and polyfluorine resin are pre-treated in a highly alkaline medium at a high temperature, and the mixture is well stirred. Suspension agent(s), water and initiator(s) are added after the temperature of the mixture has been reduced. The polymerization of the resultant mixture is carried out after it has been stirred again and become homogeneous. Thereafter, the polymerized mixture is neutralized, washed and dried, and special material having properties of both polyvinyl chloride and polyfluorine resin is formed. 
     It has now been found that the graft copolymers of the present invention may be prepared by a process whereby vinyl chloride monomer, polyfluorine resin, suspension agent(s) and water are mixed, stirred and homogenized, and initiator(s) are subsequently added to the mixture. It has been found that if the initiator(s) are added prior to the addition of water and suspension agent(s), some of the monomer will undergo polymerization, resulting in imperfect reaction or coagulating. 
     The weight proportion of polyfluorine resin to vinyl chloride monomer in accordance to the present invention is in the range of greater than 0 and up to 1 by weight. The greater the addition proportion, the better will be the physical properties of these substances. 
     The polyfluorine resin used in accordance to the present invention may be a polymer comprising one or several of the following: polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinylfluoride, polyfluorovinylidene and hexafluoropropylenetetrafluoroethylene copolymer. 
     Suitable alkaline substances to be substance employed in this invention include hydroxides or oxides of alkaline or alkaline earth metals, e.g., sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium oxide, calcium hydroxide, barium hydroxide, magnesium hydroxide and calcium oxide. The amount used is about 10% to 45% by weight based on the weight of the vinyl chloride monomer. The temperature of the system for pre-treatment preceding the polymerization step of the present invention is maintained at a range of 25° C. to 90° C., while the temperature at which the polymerization reaction is conducted is in the range of 25° C. to 80° C. Strict control of temperature of the system is preferred in order to maintain a precise degree of polymerization. 
     The agitation speed for polymerization of the present invention may be between 500 and 1000 r.p.m., and preferably is between 600 and 850 r.p.m. 
     Suitable initiator(s) used in the method of this invention are oil-soluble agents which contain organic peroxide and azo-compound groups and may be employed in the system in any combination; peroxides, azo-compounds, and combinations thereof are equally suitable. The amount of an initiator to be used is from 0.01% to 0.1% by weight based on the weight of the monomer vinyl chloride. 
     Suitable organic peroxides include lauroyl peroxide, 2,4-dichlorobenzoyl peroxide, diisopropyl peroxy dicarbonate, cumyl peroxyneodecanoate, acetyl cyclohexylsulfonyl peroxide, di-(methoxy isopropyl)peroxydicarbonate, di-(2-ethoxyethyl)peroxydicarbonate, t-butyl peroxypivalate, stearoyl peroxide, succinic acid peroxide, and benzoyl peroxide. 
     Suitable azo-compounds include αα&#39;-azo-bis-dimethyl valeronitrile, αα-azo-bis-iso-butyronitrile and 2,2&#39;-azo-bis-2,3,3-trimethylbutyronitrile. 
     Suitable suspension agents of the present invention include anionic surfactants, nonionic surfactants and dispersants. 
     Suitable dispersants include cellulose derivatives like methyl cellulose, hydroxypropyl methyl cellulose, carboxy methyl cellulose, ethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose, and synthetic polymers such as polyvinyl alcohol and polyvinyl pyrrolidone, and natural polymers such as starch and gelatine. 
     Suitable anionic surfactants include sodium lauryl sulfate, sodium lauryl ether sulfate, sodium dodecyl benzene sulfonate, sodium alkyl benzene sulfonate, sodium hydroxyl sulfonate, sodium alkyl sulfonate, and the corresponding potassium salts, and similar compounds. 
     Suitable nonionic surfactants include glycerine ester of fatty acid, sorbitan ester of fatty acid, derivatives of polychloroethylene, and condensation products of fatty acids such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate, glycerol monostearate, and glycerol monopalmitate. 
     The above-listed suspension agents may be used alone or in combination, with combinations being preferable. The amount of suspension agent(s) employed to obtain the desired results may be in the range of 0.10% to 1.0% by weight based on the weight of the monomer vinyl chloride. 
     The proportion of water to the monomer vinyl chloride in the method of this invention is 1.5 to 10% by weight, and water used must have undergone deionization treatment. 
     The following examples are given as specific illustrations of the invention. It should be understood, however, that the invention is not limited to the details set forth in the examples. 
    
    
     EXAMPLE 1 
     1000 cc of 45% sodium hydroxide, 1 g of cetyl alcohol and 175 g of polytetrafluoroethylene resin were placed into a 20 liter capacity, stainless-steel polymerization vessel (reactor) fitted with an agitator. The vessel was then evacuated to 700 mm Hg; thereafter, 3.5 l of vinyl chloride monomer were added to the vessel. The mixture thus prepared was stirred at 60° C. for 4 hours. The inside temperature of the vessel was then lowered to room temperature and 5 g of methyl cellulose, 6 g of polyvinyl alcohol, 6 l of deionized water, 1 g of 98% 2,2&#39;-azo-bis-2,4-dimethyl valeronitrile and 1.4 g of 75% di-2-ethyl hexyl peroxydicarbonate were then added to the mixture. The mixture was again stirred for half an hour and inside the temperature of the vessel was raised to 58° C., at which temperature the polymerization of the mixture was conducted until the pressure drop inside the vessel reached 6 Kg/cm.sup. 2. At this point, the polymerization was stopped and the residual vinyl chloride monomer was recovered from the mixture. The contents of the vessel were then neutralized, washed and dried. The physical properties of the resulting graft product are set forth in Table 1 that follows the comparison Example 1. 
     EXAMPLE 2 
     1000 cc of 45% sodium hydroxide, 1 g of cetyl alcohol and 95 g of polytetrafluoroethylene resin were placed into a 20 liter capacity, stainless-steel polymerization vessel (reactor) fitted with an agitator. The vessel was then evacuated to 700 mm Hg, after which 3.5 l of vinyl chloride monomer were added to the vessel. The mixture thus prepared was stirred at 60° C. for 4 hours. The inside temperature of the vessel was next lowered to room temperature and 4.5 g of the methyl cellulose, 4.8 g of the polyvinyl alcohol and 6 l of deionized water were added to the mixture. To the mixture were then added 1 g of 98% 2,2&#39;-azo-bis-2,4-dimethyl valeronitrile and 1.4 g of 75% di-2-ethyl hexyl peroxydicarbonate, and the mixture was stirred for half an hour. The inside temperature of the vessel was then raised to 58° C., at which temperature the polymerization of the mixture was conducted until the pressure drop inside the vessel reached 6 Kg/cm 2 . At this point, the residual vinyl chloride monomer was recovered from the mixture. The contents of the polymerization vessel were next neutralized, washed and dried. The physical properties of the resulting graft product are set forth in Table 1 that follows the comparison Example 1. 
     COMPARISON EXAMPLE 1 
     8 l of water, 0.8 g of methyl cellulose, 2.8 g of polyvinyl alcohol, 0.4 g of cetyl alcohol, 0.8 g of 98% 2,2&#39;-azo-bis-2,4-dimethyl valeronitrile and 1.2 g of 75% di-2-ethyl hexyl peroxydicarbonate were added to the 20 liter capacity, stainless-steel polymerization vessel fitted with an agitator. The vessel was then evacuated to 700 mm Hg, thereafter 4.5 l of vinyl chloride monomer was added to the mixture. The mixture was next stirred for half an hour. The vessel was heated to 58° C., at which temperature the polymerization of the mixture was conducted until the pressure drop of the vessel reached 6 Kg/cm 2 . At this point, the residual vinyl chloride monomer was recovered and the contents of the polymerization were then dehydrated. The physical properties of the resulting graft product are set forth in the following Table 1. 
     
                       TABLE 1______________________________________        EXPERIMENT NO.                          Com-                          pari-                          son          Exam-   Exam-   Exam-          ple     ple     ple   TestingPhysical property          1       2       1     Method______________________________________Amount of Polyfluorine          175      95      0resin added (g)Polymerization tempera-  58           58      58ture (°C.)Chlorine content (%)          54.93   55.54   56.8Amount of plasticizer          15.83   18.77   21.65absorbed (%)Bulk density   0.53    0.51    0.51(g/c.c.)Specific Viscosity           0.316   0.338   0.354Particle Size    +42 mesh  1.28    0.07  0.01Distribution    +60 mesh  2.80    0.15  0.03(%)      +80 mesh  7.10    8.05  10.00    +100 mesh 12.95   15.73 32.00    +150 mesh 45.58   44.60 49.20    +200 mesh 22.44   20.78 7.83    +325 mesh 6.90    10.04 0.90    -325 mesh 0.95    0.62  0.03Impact strength          6.01    4.95    4.51  ASTM(Kg · cm/cm.sup.2)          D-256-78Resistance to solvability          Excel-  Good    Poor  Note 1          lentGelation temperature (°C.)          140     149     160   ASTM                                D-2538-79Gelation torsion (M. gr.)          3700    3550    2950  ASTM                                D-2538-79Taber type abrasion test           47      64      98   Abrasion(abrasion wear                       wheel:mg/1000 rev.)                        H-22 load                                1000 gTensile strength          1.72    1.85    2.01  ASTM                                D-638-77aElongation (%) 177     234     380   ASTM                                D-638-77a______________________________________ 
    
     EXAMPLE 3 
     1000 cc of 45% sodium hydroxide, 1 g of cetyl alcohol and 175 g of polytetrafluoroethylene resin were charged to a 20 liter capacity, stainless-steel polymerization vessel fitted with an agitator, with 3.5 l of vinyl chloride monomer being charged last after the vessel had been evacuated to 700 mm Hg. The mixture was then stirred for 4 hours at a temperature of 60° C. After the inside temperature of the vessel had been brought down to room temperature, 5.8 g of methyl cellulose, 7 g of polyvinyl alcohol and 6 l of deionized water were next introduced into the mixture. 3.5 g of 20% cumyl peroxy neodecanoate and 2.4 g of 75% di-2-ethyl hexyl peroxydicarbonate were charged to the mixture, which was then stirred for half an hour. The vessel was heated to a temperature of 43° C. and the polymerization of the mixture was conducted until the pressure drop of the vessel reached 5 Kg/cm 2 . Residual vinyl chloride monomer was then recovered from the mixture and the contents of the vessel were neutralized, washed, and dried. The results obtained are shown in Table 2 that follows the Comparison Example 2. 
     EXAMPLE 4 
     1000 cc of 45% sodium hydroxide, 1 g of cetyl alcohol and 175 g of polytetrafluoroethylene resin were charged to a 20 liter capacity, stainless-steel polymerization vessel fitted with an agitator, with 3.5 l of vinyl chloride monomer being charged last after the vessel had been evacuated to 700 mm Hg. The mixture was then stirred for 4 hours at a temperature of 60° C. After the inside temperature of the vessel had been brought down to room temperature, 5.2 g of methyl cellulose, 6.5 g of polyvinyl alcohol and 6 l of deionized water were next introduced into the mixture. Two initiators, 3.5 g of 20% cumyl peroxydecanoate and 2.4 g of 75% di-2-ethyl hexyl peroxydicarbonate, were then charged to the mixture, which was stirred for half an hour. The vessel was heated to a temperature of 43° C. and polymerization of the mixture was conducted until the pressure drop inside the vessel reached 5 Kg/cm 2 . Thereafter, residual vinyl chloride monomer was recovered from the mixture and the contents of the vessel were then neutralized, washed and dried. The results obtained are shown in Table 1 that follows the Comparison Example 2. 
     COMPARISON EXAMPLE 2 
     8 l of deionized water, 1.2 g of methyl cellulose, 3 g of polyvinyl alcohol, 0.4 g of cetyl alcohol, 3 g of 20% cumyl peroxyneodecanoate and 1.4 g of 75% di-2-ethyl hexyl peroxydicarbonate were charged to a 20 liter capacity, stainless-steel polymerization vessel fitted with an agitator. 4.5 l of vinyl chloride monomer were next charged to the vessel after it had been evacuated to 700 mm Hg. The mixture was then stirred for half an hour. Thereafter the vessel was heated to a temperature of 43° C. at which temperature polymerization of the mixture was conducted until the pressure drop inside the vessel reached 5 Kg/cm 2 . After the residual vinyl chloride monomer had been stripped off, the contents of the vessel were dehydrated. The results obtained are set forth in the following Table 2. 
     NOTE 1 
     For the purpose of comparison, a mixture of 100 parts by weight of polyvinyl chloride resin, 2 parts of a tribasic lead sulfate, 0.8 parts of stearic acid and 40 parts of a plasticizer (DOP) was kneaded for 5 minutes on a roll. The product was then processed into a sheet and test pieces prepared therefrom were kept at 25° C. for 24 hours. Test pieces were then placed in cyclohexanone and changes associated thereof were observed. 
     
                       TABLE 2______________________________________        EXPERIMENT NO.                          Com-                          pari-                          son          Exam-   Exam-   Exam-          ple     ple     ple   TestingPhysical property          3       4       2     Method______________________________________Amount of Polyfluorine          175      95      0resin added (g)Polymerization tempera-           43      43      43ture (°C.)Chlorine content (%)          54.12   55.04   56.8Amount of plasticizer          25.62   30.79   32.4absorbed (%)Bulk density (g/c.c.)          0.48    0.42    0.34Specific Viscosity           0.490   0.505   0.530Particle Size    +42 mesh  1.01    0.87  0.02Distribution    +60 mesh  12.0    10.38 1.71(%)      +80 mesh  12.8    14.95 30.43    +100 mesh 21.71   29.36 28.74    +150 mesh 42.55   38.90 30.04    +200 mesh 9.87    5.03  7.18    +325 mesh 0.89    0.27  1.60    -325 mesh 0.04    0.20  0.29Impact strength          6.98    6.02    5.74  ASTM(Kg · cm/cm.sup.2)          D-256-78Resistance to solvability          Excel-  Good    Poor  Note 1          lentGelation temperature (°C.)          164     170     180   ASTM                                D-2538-79Gelation torsion (M. gr.)          4100    3950    3450  ASTM                                D-2538-79Taber type abrasion test           37      57      72   Abrasion(abrasion wear                       wheel:mg/1000 rev.)                        H-22 Load                                1000 gTension strength          2.05    2.30    2.54  ASTM                                D-638-77aElongation (%) 182     240     395   ASTM                                D-638-77a______________________________________ 
    
     While the present invention has been described in reference to its specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited by those illustrative descriptions, except as by the appended claims.