JPH0549694B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a novel polymer composition in which an inorganic compound and an organic polymer are strongly integrated. [Prior Art] Composite materials have been actively developed in which two or more types of materials are combined to mutually complement the properties of the constituent materials to create new effective functions. Particularly in recent years, inorganic compound powders have been used not only as fillers in composite materials, but also as powders with advanced functions added to the inorganic compounds themselves, such as ceramic materials, magnetic materials, and dental materials. Coalescence and composite materials are attracting attention. However, in this case, since the properties of the composite materials are significantly different from each other, interfacial compatibility such as compatibility and adhesiveness is poor, and composite efficiency cannot be sufficiently increased.
As a result, the essential drawback remains that the functions of the inorganic compound powder itself are difficult to fully express. Various powder surface modification methods have been proposed to improve this point and improve the interfacial affinity between organic polymer substances and inorganic compounds to achieve high filling, uniform dispersion, and high strength. For example, there are mechanochemical methods in which inorganic compounds are pulverized in the presence of reactive monomers to graft organic polymers, and radiation methods in which inorganic compounds are irradiated with high-energy radiation to graft organic polymers. Can be mentioned. However, since it requires a crushing process or a radiation generating device, it has serious problems in terms of practicality, such as complicating the process and greatly increasing manufacturing costs. In addition, as an example of a powder surface modification method using in situ polymerization of microencapsulation method, the present inventors have previously developed proposed a method of bringing a radically polymerizable vinyl monomer into contact with an inorganic compound as a third component to firmly integrate the inorganic compound and the organic polymer (Japanese Patent Laid-Open Publication No. 115412/1982). However, since this method involves non-catalytic polymerization of vinyl monomer by contacting a specific sulfonic acid monomer or sulfonate monomer with an inorganic compound, the polymerization rate of the monomer is lower than expected. It doesn't get high enough. Moreover, the publication discloses that the ratio of the organic polymer that is strongly integrated to the produced polymer, that is, the grafting efficiency, is in the range of about 79 to 88%. This value was calculated from the polymer extraction rate determined under relatively mild extraction conditions such as a 24-hour extraction test with benzene. However, extraction under more severe conditions results in lower grafting efficiency. When such polymer compositions are used in various composite materials, there is a problem that high-order interfacial affinity with organic matrices is not developed, and as a result, improvements in appearance and strength properties remain insufficient. It remained. Additionally, this method still had the problem of lack of monomer versatility in that the vinyl monomer that forms the organic polymer was limited to those whose main components were methyl methacrylate or methyl acrylate. . An object of the present invention is to provide a method for producing a polymer composition in which an organic polymer is uniformly and firmly integrated onto the surface of an inorganic compound at an extremely high polymerization rate and grafting efficiency. [Means for Solving the Problems] That is, the gist of the present invention resides in a method for producing a polymer composition in which an inorganic compound and an organic polymer are strongly integrated, which is characterized by a combination of the following requirements. : (a) suspending and dispersing an inorganic compound in an aqueous medium without using a dispersant or surfactant, and then (b) adding at least one radically polymerizable vinyl monomer to this suspended dispersion. (c) Adding to the resulting mixture a sulfonic acid or its salt represented by the following general formula [] and a radical selected from the group consisting of benzoyl peroxide, lauroyl peroxide, and azobisisobutyronitrile. and (d) polymerization by adding a polymerization initiator. general formula [Wherein, R ₁ represents H, a C ₁ to C ₂₀ alkyl group, a phenyl group and its derivatives, or a halogen atom, and X represents -CONH-,

[Formula] (In the formula, R ₂ and R ₃ each represent H or a C ₁ to C ₁₅ alkyl group, and R ₄ represents a C ₁ to C ₁₅ alkylene group). -COO( _CH2 )m (in the formula, m is a number from 1 to 20)
or (CH ₂ ) n (in the formula, n is 0 or a number from 1 to 20)
and Y represents H, NH ₄ or an alkali metal atom). R ₄ and R ₅ each represent H, a C ₁ to _{C 15} alkyl group, a halogen atom, a phenyl group, or a derivative thereof] The feature of the present invention is that the surface of an inorganic compound and the The point is that the interaction between the two is derived from strongly integrated chemical bonds that go beyond adhesion in a physical sense due to simple adsorption or van der Waals forces. The method of the present invention involves polymerization without the use of dispersants or surfactants. First, an inorganic compound is suspended and dispersed in an aqueous medium, and then at least one radically polymerizable vinyl monomer is added and mixed to this suspension and dispersion, and this mixture is used as a radical polymer to be used later. The temperature is raised to a temperature at which the polymerization initiator decomposes, and then the sulfonic acid or its salt represented by the above general formula [] (hereinafter referred to as sulfonic acid monomer) and the above-mentioned specific group are added to this mixture. By adding a selected radical polymerization initiator and stirring, an aqueous heterogeneous polymerization reaction is caused, and within a predetermined polymerization time, the inorganic material surface is coated with an extremely high polymerization rate and grafting efficiency compared to conventional techniques. A uniform and strongly integrated surface layer can be formed using the copolymer of the vinyl monomer and the sulfonic acid monomer. That is, the method of the present invention consists of a combination of the following steps, and by adopting a polymerization method that adopts a specific order of polymerization steps, an extremely high polymerization rate and high grafting efficiency can be simultaneously achieved for the first time. It is possible to: Add a vinyl monomer to a polymerization site in which an inorganic compound is suspended and dispersed in an aqueous medium without using a dispersant or surfactant, and perform radical polymerization with a specific sulfonic acid monomer. Add an initiator and carry out a polymerization reaction. For example, the inorganic compound, the sulfonic acid monomer, the vinyl monomer, and the radical polymerization initiator may be charged all at once and the polymerization reaction may be carried out without adopting the above specific order of polymerization steps, or the polymerization reaction may be carried out by charging the If an inorganic compound is preliminarily dispersed in a monomer and the surface is wetted with a vinyl monomer before polymerization is carried out, a high polymerization rate can be achieved, but a high grafting efficiency cannot be achieved. In general, in graft polymerization of a branch polymer to a trunk polymer, a high polymerization rate is achieved when graft polymerization is performed using a radical polymerization initiator, but as a result of the formation of a homopolymer, the grafting efficiency is low. It is said that the price will not increase. For example, Figure 1 of "Koubunshi" Vol. 29, March issue, p. 229 (1980) shows a relationship in which the grafting efficiency decreases as the amount of radical polymerization initiator used increases. Despite this situation, it is surprising that by employing the method of the present invention, both a high polymerization rate and a high grafting efficiency can be achieved. The sulfonic acid monomer represented by the general formula [] has a double bond as an active site that brings about polymerization activity by a radical polymerization initiator, as well as an OH group present on the surface of the resulting polymer and inorganic compound. The presence of a sulfonic acid group or a salt thereof as an active site that causes strong integration through interaction with the sulfonic acid group or its salt is essential. All compounds having structural formulas containing these functional groups can be applied to the method of the present invention. For example, 2-acrylamido-2-methylpropanesulfonic acid (hereinafter abbreviated as "AMPS"), 2-
Sodium methacrylethanesulfonate (hereinafter abbreviated as "SEM:Na"), sodium 3-methacrylpropanesulfonate (hereinafter abbreviated as "SPS"), sodium 2-propenesulfonate (hereinafter abbreviated as "NaAS") , sodium 2-methyl-2-propenesulfonate (hereinafter abbreviated as "NaMS"), etc., especially those containing an amide bond.
AMPS, SEM including ester bonds, Na and SPS
etc. are particularly preferred in that they exhibit extremely high polymerization activity and grafting efficiency (strong coalescence rate of the produced polymer). As the inorganic compound used in the present invention, all compounds that are sparingly soluble in water can be used, but among them, metals in groups 1, 2, and transition groups of the periodic table, and their oxides, hydroxides, chlorides, One or more of the following are useful: sulfates, sulfites, carbonates, phosphates, silicates and mixtures and complex salts thereof. In particular, one or more of the following are preferred because they exhibit a particularly remarkable effect on the activation of vinyl monomers and their strong integration with polymers: aluminum oxide, silicon carbide, silicon nitride,
Zirconium oxide, zirconium nitride, zirconium boride, zirconium carbide, magnesium oxide, aluminum hydroxide, calcium sulfite, calcium sulfate, silicon dioxide, antimony trioxide, talc, clay, calcium carbonate, carbon black, nickel powder, iron powder, zinc powder, copper powder, iron oxide, zinc oxide, barium sulfate, apatite, etc. As the vinyl monomer used in the present invention, any conventional vinyl monomer that can be radically polymerized can be used. Examples of the radical polymerization initiator used in the present invention include one or more radical polymerization initiators selected from the group consisting of benzoyl peroxide, lauroyl peroxide, and azobisisobutyronitrile. These are particularly effective in terms of grafting efficiency. The grafting efficiency in the present invention is a value determined as follows. - First, sample about 5 g of the reaction solution after the completion of polymerization, and quantify the amount of remaining unreacted monomer by gas chromatography using dioxane as an internal standard reagent to determine the polymerization rate, and from this, determine the amount of produced polymer. - Next, the obtained dry polymer composition is subjected to continuous Soxhlet extraction with benzene for 50 hours and then with dimethylformamide for 200 hours, and the polymer content after extraction is determined. - The amount of this polymer is defined as a true polymer that is firmly integrated with the surface of the inorganic compound through chemical bonds, and the grafting effect is calculated using the following formula. Grafting efficiency (%)=Polymer content after extraction/Amount of produced polymer×100 [Examples] Next, the present invention will be explained in more detail with reference to Examples. In addition, in the following Examples and Comparative Examples, "parts" means "parts by weight" unless otherwise specified. Example 1 and Comparative Examples 1 to 6 270.0 g of aluminum oxide as an inorganic compound was suspended in 700 ml of deionized water in a 1000 ml four-necked flask equipped with a cooling tube, nitrogen introduction tube, stirring rod, and thermocouple for detecting internal temperature. Nitrogen replacement was performed for 30 minutes in a turbid and dispersed state. Next, 28.0 g of methyl methacrylate as a vinyl monomer was added with vigorous stirring under nitrogen flow. Next, the temperature of the reaction solution was raised to 70°C in a hot water bath, and after confirming that the added monomer was uniformly dispersed, SEM・Na10.0gr was added as the sulfonic acid monomer. A solution dissolved in 20 ml of ionized water and a solution prepared by dissolving 1.0 gr of benzoyl peroxide in 2.0 gr of methyl methacrylate as a radical polymerization initiator were gradually added, and a polymerization reaction was carried out at the same temperature for 8 hours. After the polymerization was completed, about 5g was sampled from the reaction solution, and the amount of remaining unreacted monomer was determined using gas clostography using dioxane as an internal standard reagent to determine the polymerization rate. In addition, after thoroughly drying the polymer composition after the reaction at 105°C for a day and night, approximately 5 g of it was completely calcined at 650°C for 3 hours, and the amount of polymer complexed with the inorganic compound was calculated from the weight loss. I asked for it. The compounding rate (%) was calculated based on the above knowledge. [=Amount of polymer complexed with inorganic compound/Amount of polymer produced×100] For comparison, the following experiments were conducted and similar evaluations were made. The results are shown in Table 1. - In the case of a conventional non-catalytic polymerization system without adding a radical polymerization initiator (Comparative Example 1), - In the case of not adding a sulfonic acid monomer (Comparative Example 2), - The composition of the polymerization system is the same as in Example 1. However, instead of the polymerization method specified in the present invention, when all the components were charged in a flask and polymerized (Comparative Example 3), and after the inorganic compound was suspended and dispersed in deionized water, the vinyl monomer Methyl methacrylate was added to 270.0 g of aluminum oxide in advance instead of adding methyl methacrylate.
A case similar to Example 1 except that 30.0 g was mixed and impregnated with a pickling machine and used as the inorganic compound and vinyl monomer (Comparative Example 4).

[Table] The following is clear from Table 1. - Although the system shown in Comparative Example 2 in which the sulfonic acid monomer was not added showed a high polymerization rate, the composite rate was extremely low, and there was a tendency for the inorganic compound and the homopolymer to separate. - The method of the present invention (Example 1: unlike Comparative Example 1,
(adding a radical polymerization initiator),
Both the monomer polymerization rate and the compounding rate are significantly improved. - In Comparative Examples 3 and 4 in which the prescribed polymerization method was changed, the composite rate was low in both cases. For each polymer composition of Example 1 and Comparative Examples 1 to 4 shown in Table 1, methyl methacrylate-
50 with benzene, a good solvent for SEM/Na copolymer.
Table 2 shows the results of examining the decrease in polymer content by sequential extraction using a Soxhlet extractor for 50 hours with acetone and then 200 hours with dimethylformamide. Here, the polymer content after sufficient extraction with dimethylformamide for 200 hours was determined to be the grafting rate in the sense that the polymer was truly integrated onto the surface of the inorganic compound through chemical bonds. For comparison, polymethyl methacrylate,
Similar extraction operations were performed for each composition (Comparative Examples 5 and 6) coated with each polymer produced by solvent blending methyl methacrylate-SEM/Na copolymer with inorganic powder (aluminum oxide). The reduction in polymer content was compared and examined. The results are also shown in Table 2.

【table】

[Table] The following can be seen from Table 2: - Each polymer component in each composition shown in Comparative Examples 2 to 6, regardless of whether it is a polymerization type or a blend type, can be extracted by the continuous extraction operation described above. , completely extracted. This is also the case when the sulfonic acid monomer is not present in the polymerization system, or even when the sulfonic acid monomer is present, when the polymerization method specified in the present invention is not used, the produced polymer is simply attached to the surface of the inorganic compound. This indicates that the substance is merely chemically or physically adsorbed. - Comparative Example 1 shows that although some of the produced polymers were strongly integrated, the level of the grafting rate was extremely low. - In contrast, in Example 1 according to the method of the present invention, a radical polymerization initiator was added in the presence of a sulfonic acid monomer or a sulfonate monomer.・ Even when this produced polymer was subjected to a series of severe extraction operations, its extraction rate was extremely low and the grafting rate remained high. ・ Even when the polymer composition was washed with an aqueous NaOH solution, These results show a high grafting rate almost equivalent to that after the extraction operation. These results indicate that hydrogen bonding and
It was confirmed that a chemical bond type stronger than an ionic bond exists, that is, a covalent graft bond. Examples 2 to 5 In Example 1, as the sulfonic acid monomer
Instead of SEM/Na, SPS, MPS, NaAS and
Polymerization was carried out in the same manner as in Example 1 except that NaMS was used, and the grafting efficiency was measured and evaluated. The results are shown in Table 3. As is clear from Table 3, SEM/Na/SPS and AMPS showed extremely high grafting efficiency.

[Table] Example 7 and Comparative Examples 7 and 8 Except for changing the type of radical polymerization initiator,
The reaction was carried out in the same manner as in Example 1, and the results of evaluating the obtained polymer composition are shown in Table 4. As is clear from Table 4, in terms of grafting efficiency, BPO, which is a lipophilic radical initiator,
It can be seen that it is higher when LPO or AIBN is used.

[Table] Examples 8 and 9 The reaction was carried out in the same manner as in Example 1, except that the vinyl monomer shown in Table 5 was used instead of methyl methacrylate. Table 5 shows the results of evaluating the compositions. As is clear from Table 5, according to the method of the present invention, high grafting efficiency can be achieved with any vinyl monomer (Examples 8 and 9).

[Table] Example 10 Example 1 except that the type of inorganic compound was changed.
The reaction was carried out in the same manner as above, and the results of evaluating the obtained compositions are shown in Table 6. As is clear from Table 6, the method of the present invention is applicable to almost all inorganic compounds, and both the polymerization rate and grafting efficiency are significantly higher than that of conventional non-catalytic polymerization systems, and a higher degree of polymerization can be achieved. It has been shown that combined compositions can be produced.

【table】

[Table] Examples 11 to 13 and Comparative Examples 9 to 13 As a measure for evaluating the applicability of the polymer composition obtained by the method of the present invention to composite materials, polymethyl methacrylate as a matrix and Composite with polymer composition (inorganic compound content 80wt)
Table 7 shows the results of examining the appearance and bending strength of the molded products obtained by press-molding (%) at 200° C. and 20 Kgf/cm ² . As is clear from Table 7, the method of the present invention (Example
When using each of the polymer compositions obtained using 11 to 13), compared to the case where conventional polymer compositions were used, a remarkable composite effect was achieved in both the appearance and strength of the molded product. Improvement is visible.

[Table] [Effects of the Invention] According to the method of the present invention, an organic polymer can be uniformly and firmly coated on the surface of an inorganic compound with extremely high polymerization rate and grafting efficiency without the need for a particular dispersant or surfactant. The excellent effect of obtaining a polymer composition that is a higher order agglomerated composite that is unified with the above is exhibited. Furthermore, when the polymer composition obtained by the method of the present invention is used in various composite materials, molding properties are improved due to the high interfacial affinity between the polymer composition and the organic matrix. The excellent effects of improving the appearance of the product and physical properties such as strength are also exhibited.

Claims (1)

[Claims] 1. (a) An inorganic compound is suspended and dispersed in an aqueous medium without using a dispersant or a surfactant, and then (b) at least one radical polymerization agent is added to the suspended dispersion. (c) To the resulting mixture, add a sulfonic acid or its salt represented by the following general formula [], benzoyl peroxide, lauroyl peroxide, and azobisisobutyronitrile. 1. A method for producing a polymer composition in which an inorganic compound and an organic polymer are strongly integrated, the method comprising (d) polymerizing the composition by adding a radical polymerization initiator selected from the group consisting of: general formula [In the formula, R ₁ represents H, a C ₁ to C ₂₀ alkyl group, a phenyl group and its derivatives, or a halogen atom, and X is -CONH-, [Formula] (In the formula, R ₂ and R ₃ are each H or represents a _C1 to _C15 alkyl group, and _R4 represents a _C1 to _C15 alkylene group), -COO( _CH2 )m (in the formula, m is a number from 1 to 20)
or (CH ₂ )n (in the formula, n is a number from 1 to 20),
Y represents H, NH ₄ or an alkali metal atom)]. 2 The sulfonic acid monomer or its salt is 2-acrylamido-2-methylpropanesulfonic acid, 2
-Sodium methacrylethane sulfonate, 3-
Sodium methacrylethanesulfonate, sodium 2-propenesulfonate or 2-methyl-2
- The manufacturing method according to claim 1, characterized in that the sodium propenesulfonate is sodium propenesulfonate. 3. The inorganic compound is a metal selected from group ~ metals of the periodic table and transition metals, oxides thereof,
hydroxide, chloride, sulfate, sulfite, carbonate,
2. The method according to claim 1, wherein the metal compound is selected from phosphates and silicates, and mixtures and complex salts of the metal compounds.