JPS6259133B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a new block copolymer that has hot melt properties and is vulcanizable. More specifically, 2,3-dichlorobutadiene-1,
3, has a melting point within a specific temperature range, and has a specific molecular weight range, The copolymer produced by this method can form a tough film in either the unvulcanized or vulcanized state and is soluble. It is known that in copolymers of 2,3-dichlorobutadiene-1,3 and chloroprene, the former is used for the purpose of inhibiting crystallization of the resulting copolymer and improving the cold resistance of chloroprene-based elastomers in particular. It is. In this case, the proportion of the former component in the copolymer is usually 50% by weight or less according to the prior art, and the resulting copolymer does not become an elastomeric, hot-melt type polymer. Further, in Example 9 of USP 1,965,369, 2,3-dichlorobutadiene-
The results of emulsion polymerization and copolymers using a monomer charge of 1,3/chloroprene = 80/20 (weight ratio) are exemplified, except that it was impossible to form a film by air-drying the emulsion. There is no mention of the copolymer. However, the test results of the present inventors (Comparative Example 4 in this specification)
As is clear from the above, the polymer of Example 9 No. 10 was confirmed to be a complete gel polymer, so all the copolymers disclosed in USP 1965369 have soluble and hot melt properties as defined in the present invention. It is a polymer with different properties from that of a copolymer. The present inventors previously patented a novel low molecular weight copolymer of 2,3-dichlorobutadiene-1,3 and chloroprene having a number average molecular weight of 1,000 to 10,000 and a specific functional group in the molecule, and a method for producing the same. However, since the copolymer has a low molecular weight, the strength of the film obtained by simply hot-melt molding was relatively low. After that, the present inventors further conducted a detailed study on copolymers in the high molecular weight region where the molecular weight of the copolymer is 10,000 or more, and found that the monomers constituting the copolymer produced by the method of the present invention The weight composition of the body unit is within a specific range and the number average molecular weight is 20,000.
Copolymers in the range of ~500,000 contain alkyl xanthate groups, carboxyl groups, hydroxyl groups, thiol groups,
Regardless of whether or not a specific functional group such as an epoxy group or a bromine group is introduced into the molecule, (1) it maintains hot melt properties and exhibits excellent fluidity properties; (2) Easily vulcanized in the presence of a common vulcanization accelerator for polychloroprene, giving a vulcanized product with improved rubber elasticity. (3) Extremely strong films can be formed in either the unvulcanized or vulcanized state. Polychloroprene is soluble in common solvents. We discovered that the copolymer has characteristics in terms of processability, reactivity, and performance, and also confirmed that the copolymer is a unique polymer with a chain block of 2,3-dichlorobutadiene-1,3. I've reached it.
Hereinafter, the copolymer containing a 2,3 dichlorobutadiene-1,3 chain block will be simply referred to as a block copolymer. The object of the present invention is to create a so-called hot-melt polymer that is solid at room temperature due to its crystallinity, but melts when heated and has sufficient fluidity, is soluble in common solvents for polychloroprene, and is easily vulcanized. An object of the present invention is to provide a method for producing a novel block copolymer which can form a vulcanized product with improved rubber elasticity and can form a strong film in either an unvulcanized or vulcanized state. Another object of the present invention is to provide a base polymer useful as a base polymer for hot-melt film adhesives, hot-melt stretched films (heat-shrinkable), elastic vulcanized films, solvent-based adhesives, rubber-like high-hardness molded products, etc. An object of the present invention is to provide a method for producing a new copolymer. That is, in the present invention, 2,3-dichlorobutadiene-
Copolymerizing 50 to 80 parts by weight of 1 and 3, 20 to 50 parts by weight of chloroprene (100 parts by weight in total), and optionally a monomer that can copolymerize these in the presence of a chain transfer agent, The number average molecular weight of the copolymer is 20000
500,000. The copolymer produced by this method has a chain block structure of 2,3-dichlorobutadiene-1,3 and a chain block structure of chloroprene, and the weight composition ratio of the monomer units constituting the copolymer is Approximately 2,3 dichlorobutadiene-1,3/chloroprene = 60/40 to 90/10, the number average molecular weight of the copolymer is 20,000 to 500,000, and the melting point measured by differential scanning calorimeter is 80 to 130. ℃, this copolymer has hot-melt properties,
Soluble in solvent. When the average molecular weight is less than 20,000, 2,3-dichlorobutadiene in the weight composition ratio of the monomer units constituting the polymer.
If the amount of 1 and 3 is not approximately 60% or more, the crystallinity of the copolymer tends to be markedly reduced and the hot-melt properties are likely to be lost, and when a film is formed, it may be difficult to obtain a strong film. Ta. On the other hand, if the average molecular weight is too high, the hot-melt properties, fluidity properties, etc. of the polymer will be significantly reduced, making processing difficult, so it is necessary to set the average molecular weight to 500,000 or less. However, the average molecular weight is about 20,000~
A copolymer having a molecular weight in the range of about 200,000 is particularly preferable from the viewpoint of the balance between processability and performance, such as hot meltability, solubility, and mechanical strength of the film. In addition, 2,3 of the monomer units constituting the copolymer
The weight ratio of dichlorobutadiene-1,3/chloroprene ranges from approximately 60/40 to 90-10. When this weight ratio is less than approximately 60/40, that is, when the chloroprene monomer units in the copolymer increase,
The room temperature crystallinity of the copolymer decreased significantly, and the 2,3-
Since the chain block of dichlorobutadiene-1,3 disappears, the hot-melt property is lost and the mechanical strength of the unvulcanized product tends to decrease significantly.
On the other hand, if the weight ratio is greater than approximately 90/10, it approaches a homopolymer of 2,3-dichlorobutadiene-1,3 and is crystalline at room temperature, but its melting point increases and workability decreases. Moreover, it is usually extremely difficult to dissolve in organic solvents. The composition ratio of the copolymer was set in the above range in order to satisfy the above characteristics (1) to (4), which cannot be achieved simultaneously with each homopolymer of 2,3-dichlorobutadiene-1,3 or chloroprene. It is. The composition ratio of 2,3-
Dichlorobutadiene-1,3/chloroprene=
It can be said that the range of 65/35 to 80/20 is particularly preferable.
Even if the composition ratio is within this range, as the molecular weight of the copolymer increases, its solubility in toluene at room temperature tends to decrease, but dissolution becomes easier when heated to 50° C. or higher. Further, as the composition ratio becomes larger than 80/20, the solubility of the copolymer in toluene at room temperature tends to decrease. 2,3-dichlorobutadiene according to the invention
The copolymerization reaction of 1,3 and chloroprene can be easily carried out by well-known polymerization methods such as bulk polymerization, solution polymerization, or emulsion polymerization, but especially solution polymerization or emulsion polymerization is an industrial production method. It is preferable. However, when producing the copolymer using an emulsion polymerization system, which is easier to produce a high molecular weight polymer than a solution polymerization system, it is practical to select a polymerization recipe that is controlled in the presence of a relatively high level of molecular weight regulator. above is required. The reason why the copolymer produced by the method of the present invention exhibits hot melt properties, that is, relatively sharp thermal melting behavior, is due to the chain block of 2,3-dichlorobutadiene-1,3 in the copolymer. The thermal behavior results obtained using a differential scanning calorimeter (hereinafter abbreviated as DSC) and the 2,3-
This became clear from the correlation with the dichlorobutadiene-1,3 monomer composition ratio. That is, as shown in the DSC pattern in the drawing, if the weight composition ratio of 2,3-dichlorobutadiene-1,3/chloroprene in the polymerization charge is less than 50/50, 2,3-dichlorobutadiene-1,3/chloroprene
Since there is virtually no crystal structure based on the contribution of the 1,3 chain block, it has no melting point and therefore does not exhibit hot melt properties, but if the ratio is 60/40 or more, 2,3-dichlorobutadiene-1,3 A relatively sharp melting phenomenon is accompanied by the contribution of the chain block. the regularity of the chain block;
The apparent melting point of the copolymer is naturally affected by the length, etc., but in the case of the copolymer according to the present invention, it is 80
℃~130℃, especially number average molecular weight 20000
~200,000, 2,3-dichlorobutadiene-1,3/
A copolymer having a chloroprene weight composition ratio of 60/40 to 80/20 has a melting point in a range of about 80 to 110°C and exhibits excellent hot melt properties. In addition, the above 2,3-dichlorobutadiene-1,
When producing a copolymer with a weight ratio of 3/chloroprene in the range of approximately 60/40 to 80/20, each monomer of 2,3-dichlorobutadiene-1,3 and chloroprene is mixed with 50% of the former. ~80 parts by weight, the latter 20
Copolymerization may be carried out using a proportion of ~50 parts by weight (100 parts by weight in total). Further, the molecular weight of the copolymer is controlled by a chain transfer agent. Examples of chain transfer agents used include thioglycolic acid and 2-mercaptoethanol, but the chain transfer agent is not limited to these. Hot-melt properties of the copolymer produced by the method of the present invention 2,3-dichlorobutadiene-1,3
Therefore, the present invention naturally includes copolymerization in which a third component monomer is present in the polymerization system within a range that does not substantially disturb the blocking property. Examples of the third component monomer that can actually be used include styrene, acrylonitrile, acrylic acid, methacrylic acid, vinyl compounds such as vinylpyridine,
Examples include, but are not limited to, conjugated dienes such as isoprene and butadiene-1,3. In order for these monomer units not to substantially disturb the chain block of 2,3-dichlorobutadiene-1,3 in the copolymer, the weight composition of the monomer units is usually adjusted to the total polymer weight. It is desirable to keep it to 5% or less. One of the characteristics of the copolymer according to the present invention is that when it is made into a film or a molded product by utilizing its excellent hot-melt properties, it
Its mechanical strength is excellent in the unvulcanized state due to the contribution of cohesive force from the chain blocks. In addition, the copolymer can be easily heat-vulcanized in the presence of a vulcanization accelerator commonly used for vulcanization of chloroprene rubber, and has even better mechanical strength and solvent resistance than when unvulcanized. Another feature is that it can form a vulcanized product. The copolymer according to the invention has a molecular weight of 2,3-
Hot-melt properties and vulcanization reactivity vary depending on the dichlorobutadiene-1,3/chloroprene composition ratio, etc., but hot-melt properties are usually in the range of 80°C to 130°C, and in the presence of a normal chloroprene rubber vulcanization accelerator. It can be easily heat vulcanized. Of course, hot melt properties and toluene solubility are lost by heat vulcanization. In addition, if the above-mentioned specific functional groups are present in the molecule, the copolymer will exhibit the chemical reactivity of each specific functional group in addition to the vulcanization reactivity based on the constituent chloroprene polymer. Although the use of these functional groups facilitates the promotion of reactions such as chain extension, crosslinking, and formation of coordination bonds with metals, the introduction of these functional groups is not essential in the present invention and may be optional. Due to the above characteristics, the copolymer according to the present invention can be effectively used in an extremely wide range of applications. For example, molded products obtained by extrusion or roll coater using hot-melt properties are, in an unvulcanized state, hot-melt adhesives such as films, sheets, and strings, lining materials, coating materials, sealing materials, etc. It is useful for Furthermore, a film obtained by stretching an extruded film can be used as a heat-shrinkable film. When the copolymer is dissolved in a solvent,
It can be used in adhesives, paints, primers, etc. In the vulcanized state, it is useful as vulcanized films with improved elasticity, rubber-like high hardness molded products, etc. Furthermore, the copolymer can be further chlorinated as an intermediate raw material.
Modification by bromination or other post-reactions is also possible. The copolymer also has a high chlorine content of about 49.8 to about 55.2% by weight and has excellent flame retardancy, making it extremely useful as a fireproofing and flameproofing material. Further, a lamination of the copolymer film in an unvulcanized or vulcanized state can be effectively used as a gas barrier because of its low gas permeability. In addition, if necessary for practical use in the above-mentioned applications, fillers such as titanium white, calcium carbonate, clay, and carbon black, which are ordinary compound ingredients, petroleum oils, softeners such as phthalate esters, and tar, phenol resins, etc. Resins such as coumaron indene resin, petroleum-based aromatic resin, rosin acid ester resin, epoxy resin, bituminous substances such as straight asphalt, blown asphalt, and tar pitch, antioxidants such as hindered phenols, and aromatic amines, and for coloring. It is possible to blend additives, inorganic or organic fibers made of glass, alumina, steel, carbon, etc. Examples, reference examples, and comparative examples are shown below. Parts and percentages herein are based on weight unless otherwise specified. Example 1 A homogeneous mixed solution consisting of 60 parts of 2,3-dichlorobutadiene-1,3, 40 parts of chloroprene, 50 parts of toluene, and 0.5 parts of thioglycolic acid was charged into a reaction vessel equipped with a stirrer and the temperature was raised to 45°C. Thereafter, 1.5 parts of a toluene solution containing 0.5 parts of α,α'-azobis-2,4-dimethylvaleronitrile as a polymerization initiator was added to initiate polymerization. The polymerization temperature was controlled at 50℃ and the polymerization time was 3.0 hours.
1 part of toluene solution containing 0.02 part of butylcatechol was added, and the mixture was quickly cooled to room temperature to stop the polymerization. The addition rate of 2,3-dichlorobutadiene-1,3 and chloroprene to the polymer was 78.3%, respectively.
It was 55.5%. Next, the polymerization solution was treated with a thin film evaporator under reduced pressure to remove unreacted monomers, and then excess methanol was added to precipitate and isolate the polymer. The polymer was dried using a drum dryer whose roll surface temperature was controlled at 110°C to 120°C. The obtained polymer had a 2,3-
Dichlorobutadiene-1,3/chloroprene=
It is a copolymer with a composition ratio of 67.9/32.1, and when its thermal behavior was examined by DSC, it showed two melting points corresponding to the chloroprene chain and the 2,3-dichlorobutadiene-1,3 block chain. Peaks were observed around 24.5°C and 92.5°C, respectively. In particular, the peak near 92.5°C had a melting combustion value of 1.8 cal/g based on its integrated area, indicating the melting point of the copolymer. Figure 1 shows the DSC pattern of the block copolymer obtained in this example. Next, the number average molecular weight of the copolymer was measured using an everyimeter and was found to be 27,600, and the inherent viscosity [η] measured in toluene at 30°C was 0.28 dl/g. Examples 2 to 6, Comparative Examples 1 to 3 Various 2,3-
A dichlorobutadiene-1,3/chloroprene copolymer was synthesized. As a result of measuring the composition ratio, molecular weight, and DSC melting point of these, they were all hot-melt copolymers. On the other hand, in a toluene solubility test at 50°C, all the copolymers were easily soluble except for the copolymer of Comparative Example 3, which was poorly soluble. In addition, 2 in the drawing shows DSC of the copolymer obtained in Comparative Example 1.
It shows a pattern. As is clear from these results, when the 2,3-dichlorobutadiene-1,3/chloroprene composition ratio of the copolymer is 55/45 or less, the resulting copolymer is composed of 2,3-dichlorobutadiene-1,3 chains. Block properties are lost and hot melt properties are no longer exhibited. Also, if this composition ratio is 60/40 or more, 90
It was confirmed that it has a melting point near ℃ or above and exhibits excellent hot melt properties.

[Table] Example 7 A hot-melt copolymer was obtained in the same manner as in Example 4, except that thioglycolic acid was used at 0.1 part and toluene was used at 100 parts. The DCBd/CP composition ratio of this product was 77.7/22.3, the molecular weight was 143,000, and the DSC melting point was 33.0°C and 101°C. Further, when the solubility of this copolymer in toluene was measured, it was found to be poorly soluble at room temperature, but easily soluble at temperatures above 50°C. Examples 8 and 9, Comparative Example 4 Emulsion polymerization was carried out in a non-catalytic system according to the following polymerization recipe. The obtained latex was poured into a large excess of methanol, and the precipitated copolymer in the form of fine particles was isolated, air-dried, and then vacuum-dried. Table 2 summarizes the results of examining the copolymer composition, molecular weight, DSC melting point, and toluene solubility of these.

【table】

[Table] Reference example Obtained in Examples 1, 3, 4 and Comparative Example 2 above
Using DCBd/CP copolymer, various films were prepared from formulations according to the following formulations and their physical properties were measured.
The film was manufactured as follows. (1) Unvulcanized film The polymer or its blend is continuously coated in a molten state on a release paper using a roll coater with a surface temperature of 110 to 120°C, and then cooled to room temperature to a thickness in the range of 100 to 300 microns. I got the film. (2) Vulcanized film The compound is kneaded in a molten state on a paint roll with a surface temperature of 110 to 120°C, and then press-vulcanized between ferro plates. The test results are shown in Table 3. Here is test No. 7,
8 is a comparative example in which a copolymer not according to the present invention was used.

【table】 [Brief explanation of the drawing]

The figure is a schematic diagram comparing the thermal behavior (energy difference) of a copolymer according to the present invention and a control copolymer determined by a differential scanning calorimeter after correcting the baseline.

Claims (1)

[Claims] 1 2,3-dichlorobutadiene-1,3-50~
80 parts by weight of chloroprene, 20 to 50 parts by weight of chloroprene (total of 100 parts by weight), and optionally a monomer copolymerizable with these are copolymerized in the presence of a chain transfer agent to form a number average copolymer. A method for producing a block copolymer, characterized in that the molecular weight is 20,000 to 500,000.