JP2006008812A - Preparation method of aqueous dispersion of solid rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preparation method of an aqueous dispersion of a solid rubber, which realizes a latex-like liquid of the solid rubber in the form of a dispersion by dispersing solid rubber particulates in water and enables analysis such as NMR by using the latex-like liquid of the solid rubber as a sample. <P>SOLUTION: The preparation method comprises steps wherein (A) a swollen rubber is formed by swelling the solid rubber with a solvent, (B) the solid rubber particulates are formed by freezing and pulverizing the swollen rubber in the presence of a surfactant and (C) the particulates are dispersed in water. Preferably, the preparation method further comprises a step wherein (D) the solvent and/or the surfactant are separated and removed from the particulates. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for preparing an aqueous dispersion of solid rubber, and more particularly relates to a method for preparing an aqueous dispersion of solid rubber suitable as an analysis sample of physicochemical properties such as molecular structure and composition analysis of solid rubber. It is.

  In recent years, instrumental analysis equipment such as nuclear magnetic resonance (NMR) has been used to analyze the molecular structure and compositional analysis of polymer compounds, and much analysis information has been provided. It has become so.

  For example, in the measurement by NMR spectroscopy, a sample to be measured is adjusted in order to obtain a clear NMR spectrum. The object of measurement by NMR has been analyzed using various analytical samples such as liquid, solid, gas, gel, etc., but generally solid NMR is subject to many limitations compared to liquid NMR, for example, There are disadvantages in that the amount of information obtained is small due to reasons such as lower resolution than liquid NMR and fewer pulse programs used.

In the analysis of the molecular structure such as the microstructure of rubber polymer, uncrosslinked raw rubber can be analyzed using a sample that has been dissolved and liquefied in an organic solvent such as chloroform. When analyzing by NMR, the measurement using a solid high resolution NMR apparatus is tried (for example, nonpatent literature 1).
Maki Mori, J. L. Koenig "Analysis of rubber vulcanizates by high resolution NMR" Journal of the Japan Rubber Association Vol. 71, No. 2 (1998) P26-35

  However, since solid high-resolution NMR has the above-mentioned limitations, the actual structure analysis of solid rubber such as vulcanized rubber has not been performed.

  The present invention has been made in view of the above points, and in the past, solid rubber fine particles such as vulcanized rubber, which could not be liquefied before, are dispersed in water to achieve latex-like liquefaction as a dispersion. A method for preparing an aqueous dispersion of solid rubber that enables analysis such as NMR with a latex-like liquefied sample of solid rubber, and provides more analysis information such as the microstructure and crosslinking form of vulcanized rubber Is intended to provide.

  The present invention relates to a method for preparing an aqueous dispersion of solid rubber used as a sample for analysis, wherein (A) a step of swelling the solid rubber with a solvent to form a swollen rubber, and (B) the swollen rubber being a surfactant. And (C) a step of dispersing the fine particles in water, and a method for preparing an aqueous dispersion of solid rubber, comprising the steps of: freezing and pulverizing to form fine particles of the solid rubber in the presence of water.

  The method for preparing an aqueous dispersion of solid rubber of the present invention preferably further includes (D) a step of separating and removing the solvent and / or surfactant from the fine particles.

  In the present invention, when the average particle size of the fine particles of the solid rubber is 0.05 to 10 μm, the fine particles are prevented from floating and settling, the dispersibility of the fine particles in the dispersion is improved, and the solid rubber content in the dispersion is increased. Is 10 to 60% by weight, the resolution can be improved and the analysis accuracy can be increased.

  The method for adjusting the aqueous dispersion of solid rubber of the present invention is suitable when the solid rubber is a vulcanized rubber.

  According to the method for preparing an aqueous dispersion of solid rubber of the present invention, the solid rubber such as vulcanized rubber is swollen and then finely divided, so that the rubber fine particles are well dispersed in water and liquefied in a latex form. it can. This enables liquid analysis of solid rubber by NMR, etc., and has the excellent effect of being able to obtain a lot of new analysis information that could not be obtained by conventional solid analysis, and improving the performance of various rubber materials It provides many guidelines for research and has industrial effectiveness.

  Hereinafter, embodiments of the present invention will be described in detail.

  In the method for preparing an aqueous dispersion of solid rubber of the present invention, the target rubber materials include natural rubber (NR), various styrene butadiene rubbers (SBR) such as solution or emulsion polymerization, various butadiene rubbers (BR), isoprene. Diene synthetic rubbers such as rubber (IR), nitrile rubber (NBR), chloroprene rubber (CR), olefin synthetic rubbers such as butyl rubber (IIR) chlorobutyl rubber (CIIR), ethylene propylene rubber (EPM, EPDM), polysulfide rubber (T), silicone rubber (Q), urethane rubber (U), fluoro rubber (FKM), acrylic rubber (ACM), various synthetic rubbers such as chlorosulfonated polyethylene (CSM), etc. What blended in arbitrary ratios is mentioned.

  In the present invention, the solid rubber is a vulcanized rubber obtained by crosslinking the rubber material with a vulcanizing agent such as sulfur or an organic peroxide, and the sulfur of the vulcanizing agent is used for ordinary rubber vulcanization. Organic peroxides such as rubber powder sulfur and oil-treated sulfur include dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5 di ( Tert-peroxy) -hexane and the like. Moreover, what was bridge | crosslinked using vulcanizing agents, such as metal oxides, such as organic polyvalent amine, modified phenol resin, and magnesium oxide, is also used.

  The solid rubber aqueous dispersion preparation method of the present invention includes (A) a step of swelling a solid rubber with a solvent to form a swollen rubber, and (B) freezing and pulverizing the swollen rubber in the presence of a surfactant. And (C) a step of dispersing the fine particles in water, and (D) separating and removing the solvent and / or surfactant from the fine particles of the solid rubber. May be.

  (A) In the step of forming a swollen rubber by swelling a solid rubber with a solvent, about 10 to 500 mg of solid rubber pre-ground to an average particle size of about 0.5 to 5 mm is immersed in the solvent using a glass bottle or the like that can be sealed. Then swell.

  Examples of solvents used for swelling include hydrocarbons such as hexane, heptane, benzene, and toluene, alcohols such as methanol, ethanol, and acetone, and various organic solvents such as esters such as ethyl acetate and dimethyl phthalate. The solid rubber is used in an amount that can be immersed in a solvent.

  The swelling time for immersing the solid rubber in the solvent is not particularly limited, and can be determined appropriately while observing the swelling state of the solid rubber depending on the type and amount of the rubber material and the solvent, the degree of rubber cross-linking, etc. For example, the volume of the solid rubber may be about 1.3 to 2 times as a guide, and the swelling may be completed in a state where the equilibrium is almost reached.

  (B) In the step of freezing and pulverizing the swollen rubber in the presence of a surfactant to form fine particles of the solid rubber, the solid rubber swollen in the step (A) is combined with the surfactant using a freezing and pulverizing machine. It is pulverized into fine particles having an average particle diameter of about 0.05 to 10 μm. When the particle diameter is less than 0.05 μm, the dispersibility in the liquid is lowered, and when it exceeds 10 μm, the fine particles are liable to float or settle, and the dispersibility is lowered and the analysis accuracy cannot be obtained.

  Here, when freeze pulverization is performed without the addition of a surfactant, the polymer chain is cleaved and radicals are generated to cause recombination of rubber particles. Dispersibility can be improved.

  As the freeze pulverizer, a general-purpose freeze pulverizer can be used. For example, JFC-300 type manufactured by Nippon Analytical Industries, Ltd. can be used. As the freezing medium, liquid nitrogen is suitable, and 10 to 500 mg of solid rubber and a surfactant are charged into a cylindrical pulverized capsule container and pulverized until the average particle diameter is in the frozen state.

  The surfactant is not particularly limited, and is anionic such as higher fatty acid alkali salt, cationic such as higher amine halogenate, nonionic such as polyethylene glycol fatty acid ester, and amphoteric such as amino acid. In the present invention, sodium dodecyl sulfate (SDS) is preferably used.

  The amount of the surfactant used is preferably in the range of about 2 to 10 times the weight of the solid rubber (before swelling). The surfactant also has an effect as a dispersant for dispersing solid rubber fine particles in water.

  In the present invention, the dispersibility in water is improved by the interaction between the above swelling treatment and the pulverization treatment in the presence of a surfactant, that is, the solid rubber is made finer than before by the swelling treatment. Realizes and prevents rebinding of particles, and prevents surfactant particles from recombining rubber particles by eliminating the occurrence of polymer chain breakage, thereby facilitating dispersibility of rubber particles in water and making latex liquid. It is considered to be possible.

  The next step (C) in which the fine particles are dispersed in water is to add the solid rubber fine particles obtained in the step (B) to distilled water and stir to obtain a dispersion. The stirring method is not particularly limited, and a normal stirring apparatus for chemical experiments can be used.

  In this case, the amount of solid rubber added is preferably about 10 to 300 mg of rubber weight (before swelling) with respect to 5 ml of distilled water. If the amount of rubber is small, the concentration of solid rubber in the dispersion is lowered and the resolution is lowered, resulting in analysis results. If the amount of rubber is too large, the dispersibility is lowered, and the rubber component floats or settles. That is, it is desirable that the solid rubber content of the dispersion is 10 to 60% by weight, preferably 50% by weight or more.

  In the present invention, it is preferable to have a step (D) of separating and removing the solvent and / or surfactant from the fine particles of the solid rubber. By removing the solvent and surfactant used in the steps (A) and (B) from the rubber fine particles, components of the solvent and surfactant are prevented from appearing in the analysis results such as NMR spectra, and the analysis accuracy is improved. be able to.

  The solvent can be removed by once boiling a dispersion obtained by adding fine particles of solid rubber to distilled water, and the surfactant may be separated using a centrifuge to separate the mixture of fine particles and surfactant after pulverization. .

  The aqueous dispersion obtained by the method for preparing an aqueous dispersion of solid rubber according to the present invention has a latex form, and the solid rubber can be used as a liquid analysis sample such as NMR, and analysis using a conventional solid sample Thus, it becomes possible to obtain new analysis information from the vulcanized rubber, such as the crosslinked form and microstructure of the vulcanized rubber, the molecular weight of the polymer, and the molecular weight distribution, which could not be obtained.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

  Using 100 parts by weight of natural rubber (RSS # 1), 2 parts by weight of powdered sulfur for rubber (1 type specified in JIS K6222) and 1 part by weight of vulcanization accelerator CBS (specified in JIS K6202) are used. After mixing, the obtained rubber composition was press vulcanized at 150 ° C. for 30 minutes to prepare a vulcanized rubber sheet having a thickness of 2 mm. The vulcanized rubber was cut with a cutter knife into small pieces each having a size of 2 to 3 mm to prepare a granular sample of solid rubber.

  This granular rubber sample was weighed by the weight shown in Table 1, and immersed in a solvent (toluene) for 16 hours to swell, and the filtered swollen sample was pulverized capsule (volume) with sodium dodecyl sulfate (SDS) (mg) shown in Table 1. 10 ml) and pulverized into fine particles having an average particle diameter of 0.1 μm using a freeze pulverizer (manufactured by Nippon Analytical Industries, Ltd., JFC-300 type).

  Next, the dispersion obtained by adding a mixture of vulcanized rubber fine particles and a surfactant to distilled water was separated and removed using a general-purpose centrifuge, and the resulting vulcanized rubber fine particles were once distilled in 5 ml. What was added to water and stirred was boiled to remove the solvent, and then added again to 5 ml of distilled water and stirred using a stirrer to prepare a dispersion of vulcanized rubber fine particles.

  The dispersion state of the vulcanized rubber fine particles in each dispersion was visually observed and evaluated as follows. The results are shown in Table 1. (Double-circle): The favorable dispersion state was shown and it liquefied in the latex form. ○: Dispersed, but some fine particles become floating or sediment components and do not exhibit sufficient latex. X: Many floating or sedimenting components are present, indicating poor dispersion and not suitable for analysis samples.

  As shown in Table 1, a sample obtained by adding 400 mg of SDS to 50,100 mg of rubber of Experiment Nos. 5 and 8 and freeze-pulverizing exhibits a good dispersion state without causing recombination of rubber particles and is suitable as an analysis sample. I understand that.

  On the other hand, when no SDS is added or less (experiment NO1 to 3), recombination of rubber particles occurs, resulting in poor dispersion, and even if SDS is increased, the effect of improving dispersibility does not appear any more. (Experiment NO6). When the ratio of the vulcanized rubber was increased (Experiment NO9, 10), the pulverizability of the vulcanized rubber decreased and the dispersibility decreased.

The method for preparing an aqueous dispersion of solid rubber according to the present invention is an aqueous dispersion in which a solid rubber such as vulcanized rubber is dispersed in water, so that it can be used as a liquid sample for various analyzers such as nuclear magnetic resonance (NMR). Can be widely used.

Claims (4)

A method for preparing an aqueous dispersion of solid rubber fine particles used as a sample for analysis,
(A) a step of swelling a solid rubber with a solvent to form a swollen rubber;
(B) a step of freezing and pulverizing the swelling rubber in the presence of a surfactant to form fine particles of the solid rubber;
(C) The process of disperse | distributing the said microparticles | fine-particles in water. The adjustment method of the aqueous dispersion of solid rubber characterized by the above-mentioned. (D) It has the process of isolate | separating and removing the said solvent and / or surfactant from the said microparticle. The adjustment method of the aqueous dispersion of solid rubber of Claim 1 characterized by the above-mentioned. 3. The solid rubber aqueous solution according to claim 1, wherein the solid rubber fine particles have an average particle size of 0.05 to 10 μm, and the solid rubber content in the dispersion is 10 to 60 wt%. Dispersion adjustment method. The method for adjusting an aqueous dispersion of solid rubber according to any one of claims 1 to 3, wherein the solid rubber is a vulcanized rubber.