JPS62270649A - Electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain an electrically conductive resin compsn. having excellent melt flow characteristics and thermal stability, by blending a polymer obtd. by grafting vinyl chloride onto an ethylene/vinyl acetate copolymer with a vinyl chloride polymer and carbon black. CONSTITUTION:A resin compsn. is obtd. by mixing 3-90pts.wt. graft polymer having a degree of polymn. of 300-700, obtd. by grafting 98-40pts.wt. vinyl chloride onto 2-60pts.wt. ethylene/vinyl acetate copolymer having a vinyl acetate content of 10-65wt%, with a vinyl chloride polymer having an average degree of polymn. of 300-600 to obtain a resin mixture and 5-30wt% (based on the amount of the resin mixture) carbon black with the resin mixture. The degree of polymn. of the graft polymer varies depending on the purpose of use, but is 300-700 when a video disk record is to be produced therefrom. The polymn. temp. for the graft polymer is about 65-90 deg.C.

Description

Detailed Description of the Invention [Detailed Description of the Invention] (Industrial Field of Application) This invention relates to a method of graft polymerizing vinyl chloride heptamer onto a conductive resin composition, particularly a copolymer of ethylene and vinyl acetate. The present invention relates to a conductive resin composition comprising a resin mixture of the graft polymer obtained by the above method and another vinyl chloride polymer.

(Prior Art) Vinyl chloride resins have good weather resistance and excellent mechanical strength, so they are used for various molded products such as pipes, joints, and plates. Recently, attempts have been made to mix electrically conductive fillers with vinyl chloride resins to produce electrically conductive resin compositions. This conductive resin composition is said to be suitable for making capacitive video disc records.

Typical conductive fillers include fine metal powder and carbon black, of which carbon black is the most commonly used. There are many types of carbon black that can be used as a conductive filler, but Akzo's "Ketjen Black" is particularly effective in imparting conductivity and is said to be the most preferred.

As the vinyl chloride resin used to blend carbon black, in addition to polyvinyl chloride, a homopolymer of vinyl chloride, it has been proposed to use a mixture of binary copolymers of vinyl chloride and other monomers. It was done. For example, JP-A-53-115104 discloses that 44 parts by weight of a vinyl chloride copolymer containing 5% by weight of propylene, 10 parts by weight of a vinyl chloride copolymer containing 15% by weight of vinyl acetate, and 25 parts by weight of a vinyl chloride copolymer containing 15% by weight of vinyl acetate.
It states that a resin composition prepared by mixing 10 parts by weight of a vinyl chloride copolymer containing % by weight of maleic acid ester and blending a conductive filler into this mixture is suitable for making a video disc record. There is.

In addition, RCAC Belay, August 1978 issue, pages 87-115, and Japanese Patent Application Laid-Open No. 55-97034 report that homopolymers of vinyl chloride and copolymers of vinyl chloride and propylene are
It states that it is used for video disc records.

By the way, these vinyl chloride resins contain conductive fillers,
In particular, in order to impart conductivity by blending carbon black, it was necessary to blend a large amount of carbon black.

However, when such a large amount of carbon black is blended, the melt fluidity and thermal stability of the composition deteriorate, resulting in a drawback that molding becomes difficult.

(Problems to be solved by the invention) This invention improves the vinyl chloride resin while retaining the weather resistance, mechanical strength, and other vehicle frame properties of the vinyl chloride resin, and blends carbon black into the improved resin. The present invention aims to provide a resin composition which is easily molded by imparting conductivity to the resin composition and by making the resulting composition excellent in melt fluidity and thermal stability.

(Means for Solving the Problem) This inventor has produced a vinyl chloride resin that retains the good properties of vinyl chloride resin by hand and has good melt flowability and thermal stability. was planned. Then, various vinyl chloride resins were manufactured, carbon black was blended therein, and the physical properties of the resulting compositions were measured. As a result, we identified other vinyl chloride-based resins with a specific average degree of polymerization in addition to the graft polymer with a specific average degree of polymerization obtained by graft polymerizing vinyl chloride heptamer onto a copolymer of ethylene and vinyl acetate. It has been found that by adding and mixing carbon black in a specific proportion to this resin mixture, a resin composition with excellent heat resistance, good melt flowability, and good thermal stability can be obtained. Furthermore, it was found that the composition thus obtained had improved impact resistance compared to a composition containing polyvinyl chloride as the main resin. This invention was made based on such knowledge.

This invention relates to an average degree of polymerization obtained by graft polymerizing 98 to 40 parts by weight of vinyl chloride to 2 to 60 parts by weight of a copolymer of ethylene and vinyl acetate containing 10 to 65% by weight of a vinyl acetate component. A resin mixture is prepared by blending 3 to 90 parts by weight of a graft polymer of 300 to 700 with 97 to 10 parts by weight of another vinyl chloride polymer having an average degree of polymerization of 300 to 600.
This invention relates to a conductive resin composition containing 30% by weight of carbon black.

The copolymer of ethylene and vinyl acetate used in this invention is commercially available in various grades depending on the gold content of vinyl acetate, the molecular weight, and the polymerization reaction method. Generally, the higher the content of vinyl acetate, the better the compatibility with vinyl chloride.
The effect of improving impact resistance decreases, and conversely, when the content of vinyl acetate decreases, the effect of improving impact resistance improves, but the compatibility decreases. Therefore, the content of vinyl acetate in the copolymer is suitably 10 to 65% by weight.

The molecular weight of the copolymer of ethylene and vinyl acetate is expressed by the melt index or Mooney viscosity. Among these methods, the method of expressing melt index is based on ASTM
D-1238, but according to this display method, a melt index of 100 or more has good melt fluidity, but the impact resistance is insufficient, and conversely, a melt index of 0.1 or less has poor impact resistance. Although the properties are good, the melt flowability is poor. This property serves as a guideline for predicting the impact resistance or melt flowability of the graft polymer obtained when a graft polymer is obtained by graft polymerizing vinyl chloride onto a copolymer.

Furthermore, the properties of copolymers of ethylene and vinyl acetate differ somewhat depending on the polymerization method used to make them. However, when making a general conductive composition according to the present invention, it does not matter whether the copolymer is produced by a suspension polymerization method, an emulsion polymerization method, a solution polymerization method, or a high-pressure polymerization method. do not have. However, when preparing a composition for a video disc record, since impurities are contained in the interlayer, it is preferable to use a copolymer produced by a solution polymerization method or a high-pressure polymerization method, which contains fewer impurities.

The copolymer of ethylene and vinyl acetate used in this invention may contain not only ethylene and vinyl acetate components but also other monomer components. Other monomer components include various vinyl esters, such as vinyl evapropionate, vinyl butyrate, or
Vinyl esters of branched carboxylic acids having nine or more carbon atoms as shown in Japanese Patent Application No. 2741, or carbon monoxide as shown in Japanese Patent Application Laid-Open No. 48-26228 are used.

In order to graft-polymerize vinyl chloride onto a copolymer of ethylene and vinyl acetate, various methods such as an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, and a bulk type method can be used. Among these, the suspension polymerization method is preferable. This is because, according to the suspension polymerization method, fine particles that can be easily mixed uniformly with carbon black can be obtained immediately.

Methods for producing graft polymers by suspension polymerization are described, for example, in Japanese Patent Publication No. 39-27876 and Japanese Patent Publication No. 51-24391.
It is stated in the No. Specifically, ion-exchanged water, a suspension stabilizer such as polyvinyl alcohol, a radical generator, and, if necessary, a degree-of-polymerization reducing agent are placed in a jacketed polymerization reactor, and ethylene and vinyl acetate are mixed together. The copolymer is added and suspended, then the air inside the can is removed, and the cyclized vinyl is then press-fitted. Thereafter, the inside of the can is heated using a jacuit to dissolve the copolymer in vinyl chloride and initiate graft polymerization. When graft polymerization begins, heat is generated, so the jacket is cooled afterwards to reverse the polymerization to the desired point. Thereafter, unreacted vinyl chloride is collected and removed outside the can to obtain a slurry-like graft polymer. The slurry is dehydrated and sieved to obtain fine graft polymer particles.

When obtaining the graft polymer as described above, instead of using vinyl chloride alone, if other monomers are allowed to coexist with it,
A graft polymer is obtained by graft copolymerizing vinyl chloride and other monomers onto a copolymer of ethylene and vinyl acetate. The graft polymer used in this invention may be a polymer in which other monomers are graft-polymerized together with vinyl chloride. As other monomers, it is preferable to use ethylene and propylene. The content of other monomers is desirably 10% by weight or less based on vinyl chloride. When graft polymerizing vinyl chloride alone to a copolymer of ethylene and vinyl acetate, the ratio of graft polymerization is 2 to 60 parts by weight of the former copolymer and 98 to 40 parts by weight of the latter vinyl chloride. do.

The degree of polymerization of the graft polymer needs to be within an appropriate range. This is because if the degree of polymerization of the graft polymer becomes too high, the melt fluidity will deteriorate, and conversely, if the degree of polymerization of the graft polymer becomes low, the impact resistance and heat resistance will deteriorate.

The appropriate range of degree of polymerization varies depending on the intended use. For example, in cases where a large amount of carbon black is blended and precision molding is required, as in the case of video disc records, the degree of polymerization of the graft polymer must be within the range of 300 to 700. . This range is approximately 65 to
It is in the range of 90°C. Furthermore, in cases where it is sufficient to incorporate a small amount of carbon black, such as non-electrostatic packaging materials, it is advantageous to increase the degree of polymerization, since a product with higher strength can be obtained.

Other vinyl chloride polymers are mixed with the above graft polymer. Various other vinyl chloride polymers can be used. That is, not only a vinyl chloride homopolymer but also a vinyl chloride copolymer can be used. Ethylene and propylene are suitable as copolymerization partner monomers in vinyl chloride polymers. Copolymers containing these monomers are preferred because they improve melt fluidity. The ratio of vinyl chloride to other monomers in the copolymer is preferably 50% by weight or more of vinyl chloride, but 90% by weight or more of vinyl chloride and 50% by weight or more of vinyl chloride and Particularly preferred is a content of 10% by weight or less.

Other vinyl chloride polymers may be produced by any method. That is, polymers and copolymers obtained by various polymerization methods such as suspension polymerization, bulk polymerization, and emulsion polymerization can be used. It is desirable that the particle size of the other vinyl chloride polymer is approximately equal to the particle size of the graft polymer to be mixed.

This is because when the particles have the same size, it is easier to mix them together.

When mixing the graft polymer and other vinyl chloride polymers to make a grease-resistant mixture, consider the following general trends and try to obtain the specific properties required. The composition and mixing ratio of the polymer are determined. Generally, as the amount of the copolymer of ethylene and vinyl acetate increases, melt flowability and impact resistance improve, but heat resistance decreases. When the reverse is no longer the case, it shows the opposite trend to the above. In addition, if the degree of polymerization of each polymer is low, the melt fluidity will improve, but
Impact resistance decreases, and conversely, when the degree of polymerization of each polymer is high, the opposite tendency is shown. Based on these trends, the composition is determined appropriately depending on each case.

For applications aimed at video disc records, graft polymers polymerized at 65°C or higher and polymerization degrees of 300 to 60 are used.
0 vinyl chloride homopolymer or copolymer, and mix these to increase the proportion of the copolymer of ethylene and vinyl acetate contained in this resin mixture to 1 to 20% by weight.
It is desirable to do so.

To prepare a composition by blending carbon black into a mixture of the above-mentioned graft polymer and other vinyl chloride polymer, these may be mixed together and kneaded using a common mixer. Carbon brush A1 → -su! -Harmful eating #righteousness
, t, Since I have a C9 pot grinder, I need to be especially careful to mix it well and disperse it evenly. For example, it is desirable to use a mixer that can provide high shear energy, such as a Henschel mixer. Furthermore, as taught in JP-A-55-158919, it is desirable to form carbon black into fine particles of 0.044 m or less and to add these fine particles to the polyvinyl chloride resin particles in stages. As mentioned above, there are many types of carbon black, but in any case, carbon black is blended in an amount of 10 to 30% by weight based on the resin mixture.

Since the graft polymer is a vinyl chloride resin, it is easily decomposed by heating during molding. Therefore, in order to facilitate molding, it is desirable to add various auxiliary agents that have been conventionally added to vinyl chloride resins, such as stabilizers and lubricants. In addition to the auxiliary agent, a small amount of other resin can also be added. For example, resins commonly used to improve the impact resistance of vinyl chloride resins, such as methyl methacrylate-styrene-butadiene copolymer, chlorinated polyethylene, etc., can be added. Further, commonly used resins such as chill alloy (manufactured by Kanebuchi Kagaku Co., Ltd.) and PN resin (manufactured by Showa Denko Co., Ltd.) can be added to improve heat resistance. These resin addition plates contain up to 20% by weight of the resin mixture;
Preferably it is 10% by weight or less. Furthermore, when adding an auxiliary agent, particular attention must be paid to the type and amount of the auxiliary agent. This is because, for example, when used as a video disk record, if these adjuvants leached onto the stamper surface during use, clear images would no longer be obtained.

(Effects of the Invention) The composition obtained by uniformly kneading the above-mentioned mixture has electrical conductivity. Furthermore, although this composition has improved heat resistance compared to vinyl chloride homopolymers or binary copolymers, it is easy to mold and process due to its high melt flowability, and It has the property of being hard to break due to its high impact resistance. Therefore, this composition can be used in various applications that take advantage of its conductive properties. For example, since this composition does not attract dust due to electrostatic force, it is suitable for making integrated circuit cases, electrically-proof containers, and as an electromagnetic shielding material. In particular, this composition is easy to mold into a disk having fine grooves, and has high heat resistance and impact resistance, so it is suitable for video disc records. Therefore, we can expect great use in this field.

(Example) Next, the present invention will be described in detail with reference to Examples.

Example 1 First, the production of the raw material graft polymer will be explained.

Ion-exchanged water, a poval-based dispersant, an organic peroxide-based radical generator, and a copolymer of ethylene and vinyl acetate were placed in a jacketed polymerization reactor equipped with a stirrer with a pressure resistance of 60 kg/crdG and a content of 1,601 J. After charging and sealing, remaining air was removed, and then vinyl chloride and other monomers were charged and suspension polymerization was performed to produce a graft polymer.

After the polymerization reaction was completed, the remaining monomers were collected and removed, dehydrated and dried, coarse particles were removed using a 28-mesh sieve, and the remaining fine particles were collected to obtain a graft polymer. The composition and degree of polymerization of the graft polymer thus obtained are shown in Table 1 below. However, in the table below, EVA is a copolymer of ethylene and vinyl acetate, v
AC represents vinyl acetate content, and Ml represents melt index.

Table 1 Composition of graft polymer
AC26%, MI4(7) ×× Manufactured by solution polymerization method manufactured by Bayer AG, West Germany. VAC45%, Mooney viscosity 20 ×× Emulsion polymerization method manufactured by Dainippon Ink Company Manufactured by V'L,? : EVA, VAC 60%, Mll ×××× Ethylene-vinyl acetate-carbon oxide copolymer manufactured by DuPont, USA, MI 85 The above graft polymer and other chlorides shown in Table 2 The blending ratio when blending carbon black into a mixture with a vinyl polymer to form a resin composition is shown in Table 2. Table 3 for other vinyl chloride polymers. Put the graft polymer and other vinyl chloride polymer into the mixture, add carbon black while stirring, raise the temperature to 50°C to uniformly disperse, then add the above stabilizer and lubricant, Mixing was continued for 5 minutes while maintaining the temperature at 50-60°C. Thereafter, it was cooled and the blended powder was taken out. Next, 150 grams of this blended powder was kneaded using two 8-inch rolls to form a sheet with a thickness of 0.5 am.

Next, this sheet was sandwiched between herotype plates and press-molded to obtain a plate with a smooth surface and a thickness of 1 fl. In addition, test pieces for heat resistance measurement were created by press molding.
Using these, melt fluidity, heat resistance, thermal stability, bending strength, impact resistance, electrical conductivity, moisture absorption resistance, etc. were investigated. The test methods for each are as follows.

Melt fluidity 2 After cutting the above sheet into 211 m squares,
This was placed in a Koka type flow tester, and a pressure of 150 h/cyA was applied using a 1φ x Loam nozzle.

The fluidity was examined at a temperature of 180°C.

Heat resistance: Using the plate obtained by the above press molding, ASTMD
-648 (load: 18.6 kg).

Thermal Stability 2 The above sheet was heated in a gear oven at 170°C and evaluated based on the time until foaming.

Impact resistance: Test pieces were prepared by cutting a press plate with a thickness of 1 mm into a rectangle of 2σ on each side, and evaluated using a DuPont impact tester according to the following method.

Attack core +R1 Striker base flat, Weight 300 ri, Falling height: 4% 5cm.

Measurement temperature: 20°C 1 Evaluation Measurements were made on 12 test pieces, and the results were quantified using the following criteria.

0: Not broken.

1: Cracks appear.

2: Cracks but does not scatter.

3; It cracks and scatters.

Conductivity: Width 10mm, length 70mm from a press plate with a thickness of 1mm
A test piece of mm was prepared, and after polishing both ends of the test piece with sandpaper, a silver paste paint was applied thereto, and the test piece was left in a room at 20° C. and 150% RH for 24 hours. Thereafter, a DC voltage was applied to measure the volume resistivity.

Moisture absorption resistance: Three test pieces of 5 Wm square were cut out using a press plate with a smooth surface and left at 50° C. and 195% RH for 6 hours. The number of abnormal bubbles was then examined using a 40x magnification microscope.

The results of examining the above properties are shown in Table 4 below along with the composition of the resin mixture.

The following can be gleaned from Table 4. That is, from experiment numbers 6 and 8 in Table 4, as the degree of polymerization increases, melt fluidity deteriorates, but impact resistance improves. Moreover, from Experiment Nos. 5 to 7, as the ethylene and vinyl acetate copolymer component in the resin mixture increases, the impact resistance improves, but the heat resistance deteriorates. Furthermore, from Experiment No. 11, when a copolymer containing a large amount of vinyl acetate component is used, the impact resistance is not very good. Furthermore, when a copolymer of ethylene and vinyl acetate produced by emulsion polymerization is used, it becomes highly hygroscopic. In general, all of these compositions have good electrical conductivity, and can be said to have good properties when melt flowability, heat resistance, and impact resistance are taken into account.

Comparative Example 1 Using only other vinyl chloride polymers shown in Table 2,
A formulation similar to that in Example 1 was prepared, and the physical properties of the formulation were measured in the same manner. The results are shown in Table 5.

Table 5 Resins used and physical property measurement results (comparison of effects) Comparing Tables 4 and 5, it is found that copolymerization of ethylene and vinyl acetate is more effective than using other vinyl chloride polymers alone. It can be seen that the use of a mixture with a graft polymer obtained by graft polymerizing vinyl chloride is superior in melt fluidity, heat resistance, impact resistance, and thermal stability. In particular, with regard to heat resistance, it is generally said that mixing a graft polymer with a biral chloride polymer lowers the heat resistance, but when carbon black is added to this,
The content of ethylene-vinyl acetate copolymer is 2 to 10
On the contrary, heat resistance is improved as long as the weight N% is within the range. This is completely unexpected. It is unclear why such an unexpected phenomenon occurs.

However, when examining the solubility in tetrahydrofuran, the composition with improved heat resistance is poorly soluble, so it is assumed that cross-linking is generated. Specifically, conductive compositions made by adding carbon black to a vinyl chloride polymer alone or a resin composition in which an ethylene-vinyl acetate copolymer is added are easily soluble in tetrahydrofuran. . However, the composition of the present invention, in which a graft polymer is added thereto, is poorly soluble in tetrahydrofuran. Therefore, the physical properties of the composition of this invention are not simply a mixture.

As described above, the composition of the present invention has a good balance between melt flowability and other physical properties, and is therefore suitable for use in integrated circuit cases, electrically-proof containers, electromagnetic shielding materials, and other video discs that require precision molding. Suitable for manufacturing records.

Claims (1)

[Claims] 1. Obtained by graft polymerizing 98 to 40 parts by weight of vinyl chloride to 2 to 60 parts by weight of a copolymer of ethylene and vinyl acetate containing 10 to 65% by weight of a vinyl acetate component. Graft polymer 3 having an average degree of polymerization of 300 to 700
to 90 parts by weight of another vinyl chloride polymer having an average degree of polymerization of 300 to 600 to form a resin mixture, and 5 to 30% by weight of carbon black to this resin mixture is blended into a conductive resin. Composition. 2. The conductive composition according to claim 1, which uses a graft polymer obtained by polymerization at a temperature of 65-90°C or higher. 3. As the graft polymer, a graft polymer obtained by simultaneous graft polymerization of ethylene or propylene in an amount of 10% by weight or less of the vinyl chloride is used together with vinyl chloride, as described in claim 1 or 2. conductive composition.