CN111285971B - Preparation method of polyvinyl pyrrolidone/chlorinated polyethylene water-swelling rubber - Google Patents

Abstract

The invention belongs to the technical field of high-molecular graft copolymers and preparation thereof, and relates to a preparation method of polyvinyl pyrrolidone/chlorinated polyethylene water-swelling rubber. The invention firstly uses hydrophilic monomer N-vinyl pyrrolidone dissolved with initiator and cross-linking agent to swell chlorinated polyethylene rubber, and then carries out free radical polymerization to obtain the polyvinyl pyrrolidone/chlorinated polyethylene water-absorbing swelling rubber. This first swelling and then polymerizing process allows the hydrophilic polymer formed in situ to be uniformly and efficiently dispersed in the rubber matrix. Further, the preparation method obtains a graft copolymer of a rubber molecular chain grafted with a hydrophilic polymer, and a three-dimensional space network structure is formed in the presence of a cross-linking agent. The combined action of grafting and crosslinking enables the hydrophilic dispersed phase and the rubber matrix to be firmly connected together, effectively inhibits the loss of the hydrophilic polymer after soaking in water, and obviously improves the stability of the water-swellable rubber.

Description

A kind of preparation method of polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber

Technical field

The invention belongs to the technical field of macromolecular graft copolymer and its preparation, in particular to a preparation method of polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber.

Background technique

Water-swellable rubber is a composite material composed of hydrophilic material and rubber, in which rubber is used as a continuous phase, and the hydrophilic material is generally dispersed in the rubber with a micron size. After the water swellable rubber contacts water, the hydrophilic material particles in it can absorb water and cause the volume expansion of the water swellable rubber. When the water-swelling rubber reaches the maximum water-swelling ratio. Water-swellable rubber has the characteristics of water-swelling and sealing and water-stopping. It is widely used as a sealing and leak-proof material for engineering deformation joints, construction joints, pipe joints and other projects of subways, tunnels, highways and underground buildings, as well as on-site quick plugging of dams. leak. Its research and development started in Japan in the 1970s, and then countries in Europe, America and Japan conducted in-depth theoretical and applied research on it. Although my country started late, it has made remarkable progress with the efforts of the majority of scientific researchers.

At present, there are two main methods for preparing water-swellable rubber: physical blending and chemical grafting.

Physically blended water-absorbing swellable rubber, as the name suggests, is to chop the water-absorbing material into micron-sized particles through strong shearing force, disperse in the rubber matrix, and then vulcanize and cross-link to obtain water-absorbing swellable rubber. The blending method is relatively simple and low-cost, and there are many options for both rubber matrix and water-absorbing materials. The available water-absorbing materials are: (1) natural polymer superabsorbent resin, such as starch or cellulose grafted polyacrylate, polyacrylamide; (2) synthetic superabsorbent resin, such as cross-linked poly(methyl) (3) Inorganic high sodium bentonite and its modified products. The rubber matrix is generally selected from rubber with a certain polarity, such as chlorinated polyethylene rubber, neoprene rubber, and nitrile rubber. This is to increase the interface bonding force between the rubber matrix and the water-absorbent resin and inhibit the loss of the water-absorbent resin. It is better to add a graft-type (or block-type) compatibilizer to further enhance the interfacial adhesion. However, due to the large cohesion of the water-absorbent resin itself, the compatibility with the rubber matrix is poor, and the dispersion in the rubber matrix is not good; and there is no chemical bond between the water-absorbent resin and the rubber matrix, so it is easy to be immersed in water. As a result, the water swelling rate and mechanical properties are getting worse and worse with the use of time.

The chemical graft type water-swellable rubber is obtained by grafting the hydrophilic polymer chain to the rubber molecular chain through chemical reaction. Compared with the blended type, the water-absorbent resin has good dispersibility, strong interfacial bonding force with the rubber matrix, and strong water-swelling stability. CN201410122582 discloses a preparation method of a graft-modified chlorine-containing polymer film with durable hydrophilicity. The method of this patent application is to first remove HCl from the chlorine-containing polymer chain with a strong base to form an unsaturated bond on the chain, and then graft a hydrophilic polymer on the chlorine-containing polymer chain through a free radical polymerization reaction. The disadvantages of this method are that the grafting rate is low (more hydrophilic homopolymers are generated), the steps are cumbersome and the cost is high.

SUMMARY OF THE INVENTION

Previous research results show that chlorinated polyethylene can be swelled by some olefinic monomers, and then free radical polymerization is initiated. During the polymerization process, free radical chain transfer occurs to form chlorinated polyethylene graft copolymers. Inspired by this, the inventors of this case discovered that a hydrophilic monomer—N-vinylpyrrolidone (NVP)—can swell chlorinated polyethylene rubber in a wide range of composition ratios, and subsequently initiate its polymerization to generate water absorption. Expanded rubber.

The object of the present invention is to avoid the deficiencies in the above-mentioned prior art and provide a preparation method of polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber. The object of the present invention is achieved through the following technical solutions:

1. a preparation method of polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber, is characterized in that the preparation method is:

Azobisisobutyronitrile and 1,6-hexanediol diacrylate were dissolved in N-vinylpyrrolidone, and then azobisisobutyronitrile and 1,6-hexanediol diacrylate were dissolved N-vinylpyrrolidone and chlorinated polyethylene rubber were put into the reactor, mixed uniformly, deaerated with nitrogen, heated to 70°C, and reacted for 6 hours. Vacuum dried to constant weight to obtain polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber.

2. the preparation method of polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber according to claim 1, is characterized in that: the mass ratio of described N-vinylpyrrolidone and chlorinated polyethylene rubber is 1:4 ~1:2.

3. The preparation method of polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber according to claim 1, wherein the azobisisobutyronitrile is 0.5 mol% of N-vinylpyrrolidone.

4. the preparation method of polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber according to claim 1, is characterized in that: described 1,6-hexanediol diacrylate is 1 of N-vinylpyrrolidone ~3 mol%.

In the above technical scheme, chlorinated polyethylene rubber (CPE) is a rubber with relatively strong polarity, and it has a relatively strong interaction with polar polyvinylpyrrolidone (PVP), and the compatibility of the two is good. , so it can improve the stability of water-swellable rubber.

The hydrophilic monomer—N-vinylpyrrolidone—is able to swell chlorinated polyethylene rubber in a relatively wide range of composition ratios, which means that the N-vinylpyrrolidone is evenly distributed in the rubber matrix, so that it can pass through free radicals. The polyvinylpyrrolidone hydrophilic dispersed phase is formed in-situ within the rubber matrix by polymerization. This in-situ polymerization process can make the hydrophilic phase relatively uniformly dispersed, and the dispersed phase size is small. Moreover, in the process of in-situ radical polymerization, the primary radicals (or propagating radicals) are chain-transferred to C-Cl bonds on the rubber molecular chain to form rubber/polyvinylpyrrolidone graft copolymers. The graft copolymer can increase the interfacial bonding force between the hydrophilic dispersed phase and the rubber matrix, inhibit the loss of hydrophilic components, and improve the stability of the water-swelling rubber.

1,6-Hexanediol diacrylate is a diene-based cross-linking agent with flexible chains. After adding, it will generate a three-dimensional network structure of hydrophilic polymers. Its function is to control the expansion rate of water absorption, and the other function is to inhibit the hydrophilicity Loss of components, increased stability. Through the joint action of chain transfer and diene cross-linking agent, the CPE rubber matrix is not only cross-linked to a certain extent, eliminating the need for a special vulcanization step, but also the hydrophilic dispersed phase and the rubber matrix are cross-linked into a whole, which greatly increases the Stability of polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber.

The hydrophilic monomer N-vinylpyrrolidone inevitably forms a small amount of free oligomers during the in-situ radical polymerization process. From the point of view of polymer physics, only the crosslinking structure determines the water swelling performance, while the free oligomers Nothing works. Therefore, after the polymerization is completed, the free oligomers are removed by rinsing with deionized water.

Compared with the prior art, the present invention has the following advantages:

(1) In the present invention, the CPE rubber matrix is swelled with a hydrophilic ethylenic monomer, and then free radical polymerization is initiated inside the swollen rubber, that is, the hydrophilic polymer is formed in-situ in the rubber matrix. This process enables the generated hydrophilic polymer to be uniformly dispersed in the rubber matrix, and the size of the hydrophilic dispersed phase is small.

(2) In addition, the C-Cl bond on the molecular chain of the CPE rubber is relatively weak, and it is easy to cause chain transfer between free radicals (or growth free radicals), so that in the process of free radical polymerization in the swollen rubber matrix, it can be A CPE/PVP graft copolymer is formed. Relying on the existence of the graft copolymer, the bonding force between the hydrophilic phase of the hydrophilic polymer and the rubber matrix phase is strengthened, thereby inhibiting the loss of the hydrophilic polymer during the process of water absorption and swelling, and improving the stability.

(3) The preparation method of the water-swellable rubber of the present invention has relatively simple process, moderate water-swelling rate of the product, good mechanical properties after water-swelling, and can be used for waterproofing and water-stopping and leak-stopping in various civil engineering and construction processes.

Detailed ways

The following examples are intended to further illustrate the present invention, but not to limit the scope of the present invention.

Examples 1-4

Azobisisobutyronitrile and 1,6-hexanediol diacrylate were dissolved in N-vinylpyrrolidone, and then azobisisobutyronitrile and 1,6-hexanediol diacrylate were dissolved N-vinylpyrrolidone and chlorinated polyethylene rubber were put into the reactor, mixed uniformly, deoxygenated with nitrogen, heated to 70°C, reacted for 6 hours, the product was taken out, washed in deionized water for 120 hours, and dried under vacuum at 60°C to Constant weight to obtain polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber.

The preparation method of the polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber of Examples 1-4, the implementation method is the same, but wherein azobisisobutyronitrile, 1,6-hexanediol diacrylate and chlorinated polyethylene The weight ratio (or molar ratio) between rubbers is different. The composition ratios of Examples 1-4 are shown in Table 1.

The hardness of the sample after water swelling is tested according to the standard GB/T531-2008, and the tensile strength and elongation at break of the sample after water swelling are tested according to the standard GB/T528-2009.

Water absorption expansion ratio test: the size of the sample is 20mm×20mm×2mm, weigh its original weight, soak the sample in deionized water, take out and weigh at different soaking times, and quickly dry the surface with filter paper before each weighing Moisture, repeat the operation until the mass of the weighed soaked sample does not change, that is, the sample reaches the equilibrium of water absorption and swelling. The formula for calculating the water swelling ratio is as follows:

Water absorption expansion ratio = (water absorption balance weight - original weight of the sample) / original weight of the sample × 100%

Mass loss rate test: the sample size is 20mm×20mm×2mm, weigh its original weight, soak the sample in deionized water for 120 hours, change the water every 24 hours, and then take out the sample and place it in a 60°C vacuum drying oven After drying to constant weight, the formula for calculating the mass loss rate of the sample is as follows:

Mass loss rate = (original weight of sample - weight of sample after water absorption and drying)/original weight of sample × 100%

The test results are shown in Table 1.

Table 1

Claims (4)

1. A preparation method of polyvinyl pyrrolidone/chlorinated polyethylene water-swelling rubber is characterized by comprising the following steps: dissolving azodiisobutyronitrile and 1, 6-hexanediol diacrylate in N-vinyl pyrrolidone, then putting the N-vinyl pyrrolidone in which azodiisobutyronitrile and 1, 6-hexanediol diacrylate are dissolved and chlorinated polyethylene rubber into a reactor, uniformly mixing, introducing nitrogen to remove oxygen, heating to 70 ℃, reacting for 6 hours, taking out a product after the reaction is finished, soaking and washing the product in deionized water for 120 hours, and drying in vacuum at 60 ℃ to constant weight to obtain the polyvinyl pyrrolidone/chlorinated polyethylene water-absorbing expansion rubber.

2. The method for preparing polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber according to claim 1, characterized in that: the mass ratio of the N-vinyl pyrrolidone to the chlorinated polyethylene rubber is 1: 4-1: 2.

3. The method for preparing polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber according to claim 1, characterized in that: the azodiisobutyronitrile accounts for 0.5mol percent of the N-vinyl pyrrolidone.

4. The method for preparing polyvinylpyrrolidone/chlorinated polyethylene water-swellable rubber according to claim 1, characterized in that: the 1, 6-hexanediol diacrylate accounts for 1-3 mol% of the N-vinyl pyrrolidone.