JPH11147911A - Process for removing residual monomer from granular vinyl chloride paste resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a residual monomer from a granular vinyl chloride paste resin without detriment to the quality of the resin by bringing the paste resin into further contact with an air stream in a specified temperature range. SOLUTION: A granular vinyl chloride paste resin obtained by drying a polymer latex produced from a monomer mixture based on a vinyl chloride monomer is brought into further contact with an air stream at 20-60 deg.C. The size of the granular vinyl chloride paste resin is desirably such that the mean article diameter is 30-100 μm, further 30-80 μm, particularly 30-70μm. By bringing the granular paste resin into contact with an air stream at 20-60 deg.C, desirably 30-50 deg.C its residual monomer content can be decreased to, desirably, 5 ppm or below, more desirably, 1 ppm or below. Although the time of contact with the air stream may vary with various conditions, it is usually about 10 to 360 min. The contacting system adopted is, for example, a fluidized bed system which may be batchwisc or continuous.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a granular vinyl chloride paste resin (hereinafter also referred to as a granular paste resin).
For removing residual monomers. More specifically, a method for efficiently removing residual monomers from a granular paste resin by contacting a granular paste resin obtained by drying a vinyl chloride resin latex for paste with an airflow at 20 to 60 ° C. About.

[0002]

2. Description of the Related Art Vinyl chloride paste resin (hereinafter also referred to as paste resin)
Is dispersed in a plasticizer at room temperature to form a plastisol,
The plastisol is heated and gelled through processes such as coating to produce processed products such as wallpaper and flooring.

[0003] This paste resin is obtained by drying a polymer latex obtained by subjecting a monomer mixture mainly composed of a vinyl chloride monomer to emulsion polymerization or fine suspension polymerization in an aqueous medium.

[0004] As the paste resin, a spherical (granular) resin of 30 µm or more obtained by spray-drying latex is preferably reduced to about 0.1 to 10 µm because it is easily dispersed in a plasticizer to form a plastisol. Only ground powders were used, but the disadvantages of powders are:
In order to improve the work environment due to the generation of dust when opening the product bag, and to improve problems such as the inability to automatically weigh and supply the powder, the latex was dried at an air inlet temperature of 100 ° C.
Hereinafter, a method has been developed in which the temperature of the drying air outlet is set to 53 ° C. or lower, and a granular resin having an average particle size of 30 to 100 μm obtained by spray drying to a moisture content of 0.1 to 0.5% is used as it is ( JP-A-2-225529), which has been well received.

However, in the case of the powdery material crushed to a size of about 0.1 to 10 μm, a problem is caused in that the vinyl chloride monomer contained in the crushing is removed to some extent and the vinyl chloride monomer remains. In the case of using a granular paste resin of 30 μm or more obtained by spray drying as it is, the vinyl chloride monomer (usually several tens ppm or more) contained in the resin is positively used. There is no step to be removed and remains in the granular paste resin.
The residual vinyl chloride monomer contaminates the atmosphere of the processing plant during the molding of the paste resin, and also remains in the paste processed product obtained by the processing, and impairs the health of the user of the molded product. And so on.

[0006] The residual monomer is gradually reduced by allowing the granular paste resin to stand and store.
If the storage is not carried out for an extremely long time, the amount of the residual monomer cannot be reduced, which is not preferable from the viewpoint of production and efficiency.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to remove residual monomers from a granular paste resin without impairing the quality of the resin. A granular vinyl chloride-based resin characterized by further contacting a granular vinyl chloride-based paste resin obtained by drying a polymer latex produced from a monomer mixture as a main component with an air stream at 20 to 60 ° C. The method for removing residual monomers according to claim 1, wherein the method for removing residual monomers from the paste resin (Claim 1) and the average particle size of the granular vinyl chloride paste resin are in the range of 30 to 100 µm. (Claim 2).

[0008]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a granular paste resin obtained by drying a polymer latex produced from a monomer mixture mainly composed of a vinyl chloride monomer is used.

The monomer mixture mainly composed of the vinyl chloride monomer is defined as a monomer containing at least 50% (% by weight, the same applies hereinafter) of the vinyl chloride monomer, and more preferably at least 80% to 100%. This is a body mixture, and can be used without any particular limitation as long as it is a monomer mixture conventionally used in the production of a vinyl chloride paste resin.

The monomers other than the vinyl chloride monomer contained in the monomer mixture mainly composed of the vinyl chloride monomer include, for example, olefins such as ethylene and propylene, vinyl acetate and vinyl stearate. Vinyl esters, acrylates such as methyl acrylate and methyl methacrylate, esters and anhydrides of acids such as maleic acid or fumaric acid, nitrile compounds such as acrylonitrile, and vinylidene compounds such as vinylidene chloride. . These may be used alone or in combination of two or more.

The polymer latex is produced by emulsion polymerization or fine suspension polymerization of the monomer mixture in an aqueous medium, and is conventionally produced for producing a vinyl chloride paste resin. As long as it is the same as that described above, it can be used without particular limitation.

[0012] The above-mentioned emulsion polymerization uses an anionic surfactant and / or a nonionic surfactant as an emulsifier, and comprises a water-soluble peroxide or a combination of a water-soluble peroxide and a water-soluble reducing agent. Or using a combination of an oil-soluble peroxide and a water-soluble peroxide as a polymerization initiator, if necessary, in the presence of other polymerization aids, in an aqueous medium in the presence of the vinyl chloride-based monomer mixture Are polymerized to have an average particle diameter of 0.1.
Emulsion polymerization to produce fine particles of 1 to 0.4 μm, and emulsion polymerization in the presence of a vinyl chloride resin which has been prepared in advance as seed particles, thereby enlarging the seed particles as nuclei to form 0.4 to 2 μm Seeding emulsion polymerization that produces relatively large particles is included.

The fine suspension polymerization is, for example, a method in which a monomer mixture mainly composed of vinyl chloride, water, an emulsifier, a polymerization initiator soluble in a monomer, and other polymerization auxiliaries are mixed with a polymerization apparatus other than a polymerization apparatus. After homogenizing under high shear in the apparatus, transfer to a polymerization apparatus and polymerize under stirring, and the average diameter of the resin is 0.2 to 5 μm.
This is a method for producing fine vinyl chloride resin particles of about m.

The polymer latex is preferably spray-dried by the method described in JP-A-2-225529, for example, to obtain a water content of preferably 0.1 to 0.1%.
5%, average particle size 30-100 μm, further 30-70
μm, a granular paste resin having a residual monomer content of several tens ppm.

As a specific example of the spray dryer, for example, “Spray Drying Handbook (SP)
RAY DRYING HANDBOOK) "
Written by K. Masters, 3rd edition, 197
Nine years, George Godwin (George Go)
dwin Limited), page 121, 4th
・ Various spray dryers as shown in FIG.

When granulating the polymer latex with a spray drier, the polymer latex is first sprayed with an atomizer in a spray drier and then dried to produce a granular paste resin, which is taken out of the system. You. The higher the drying temperature at this time, the longer the time required to disperse the obtained granular paste resin in the plasticizer.

When the polymer latex is dried and granulated by a spray drier, the inlet temperature of the drying air is set to 100.
C. or lower, preferably 60.degree. C. or higher, and the outlet temperature is 53.degree. C. or lower, more preferably 50.degree. C. or lower, and preferably 40.degree. C. or higher.

The drying air inlet temperature refers to the temperature of the drying air at the dryer inlet, and the outlet temperature refers to the air temperature at the dryer outlet.
This is the temperature measured by a normal thermometer.

When the inlet temperature of the drying air exceeds 100 ° C. or the outlet temperature exceeds 53 ° C., the time required for dispersing the obtained granular paste resin in the plasticizer becomes long.

When the spray dryer is large, for example, when the tower length exceeds 5 m, the residence time of the granular paste resin is inevitably long, so that the outlet temperature of the dryer is kept at about 50 ° C. This is preferred from the viewpoint of dispersibility of the obtained granular paste resin in a plasticizer.

Next, regarding the size of the granular paste resin, it is preferable that the diameter of the granular paste resin is large from the viewpoint of improving the powder characteristics. Is preferably 30 to 100 μm, more preferably 30 to 80 μm, and particularly preferably 30 to 70 μm.

As described above, the resin has the same sol-forming property as the finely ground paste resin conventionally used, and deteriorates the working environment due to the generation of dust at the time of opening the bag of the resin and the powder. Solved problems such as the inability to automatically meter in the average particle diameter of 30 to 100 μm, the residual monomer content of several tens of ppm, and the angle of repose, which is one of the indexes of the powder characteristics, of 30 to
When it is evaluated by a method for measuring the size of the undispersed substance in the sol described later, the size of the undispersed substance is usually about 30 degrees.
A granular paste resin having characteristics such as about μm or less is produced.

In the present invention, the granular paste resin produced by the method as described above is further treated at 20 to 60 ° C.
Preferably, the residual monomer content is reduced to preferably 5 ppm or less, more preferably 1 ppm or less by contacting with an air stream at 30 to 50 ° C.

The granular paste resin has an average particle size of 0.1.
~ 5μm basic particles gathered together,
The removal rate of the residual monomer in the granular paste resin can be arranged by the diffusion of the residual monomer from the basic particles and largely depends on the diameter of the basic particles. The smaller the basic particle diameter, the higher the removal rate of the residual monomers This has been clarified by the present inventors' research. Further, since the residual monomer removal rate can be arranged by diffusion, the higher the treatment temperature, the larger the diffusion coefficient and the higher the removal rate.

Since the granular paste resin produced by the method of the present invention is a paste processing resin, it is necessary that the resin has favorable characteristics (such as sol-forming properties) as the paste processing resin.

[0026] The higher the temperature of the gas stream brought into contact with the granular paste resin, the higher the rate of removal of residual monomers from the granular paste resin, but if the temperature of the gas stream exceeds 60 ° C, the aggregation of the granular paste resin will occur. When a sol is produced using such a resin and paste processing, especially coating processing, a coating film having a smooth surface cannot be obtained. The paste sol itself may not be obtained depending on the airflow temperature. On the other hand, when the airflow is lower than 20 ° C., the efficiency of removing residual monomers is low.

Further, the time during which the granular paste resin is brought into contact with the air flow varies depending on the temperature, the absolute humidity, the air flow, etc. of the air flow, and the allowable amount of the monomer remaining in the obtained granular paste resin is also considered. However, it is usually 10 to 360 minutes, preferably 10 to 200 minutes, and more preferably 20 to 120 minutes.

The method for bringing the granular paste resin into contact with the gas stream is not particularly limited as long as the granular paste resin and the gas stream are sufficiently contacted. For example, there is a method in which a fluidized bed is formed and brought into contact with the gas stream. However, phenomena such as channeling (a phenomenon in which a local flow path is formed in a fluidized bed) and slugging (a phenomenon in which an air flow discontinuously flows as bubbles) due to the granular paste resin flowing uniformly in the apparatus. It is preferable to minimize the occurrence of As a method, for example, a method (batch (batch) type) in which a predetermined amount of granular paste resin is charged in a processing apparatus in advance, then processed for a predetermined time under the above-mentioned conditions, and taken out at the end of the processing, or A method in which a granular paste resin is charged into the apparatus and a desired residence time is given, and then the resin is continuously withdrawn (continuous method) or a method in which a batch method and a continuous method are connected in multiple stages may be used.

Next, the granular paste resin obtained by drying the polymer latex is brought into contact with an air stream,
An apparatus for reducing the residual monomer content will be described with reference to FIGS.

FIG. 1 shows a batch type fluidized bed type monomer removing apparatus.

In FIG. 1, 1 is a fluidized bed container, 2 is a dispersion plate (punched metal), 3 is a fluidized bed of granular paste resin obtained by drying a polymer latex, and h is the thickness of the fluidized bed. , 4 is an air volume adjustment valve, 5 is a blower, 6
Denotes a heater, 7 denotes a dust collector, 8 denotes a suction blower, and 9 denotes a rotary valve.

When the residual monomer in the granular paste resin is removed by the batch type fluidized bed type monomer removing apparatus shown in FIG. Of the fluidized bed from the resin inlet.
The thickness h of the fluidized bed is the thickness of the resin at rest when not fluidized, and is usually preferably 1500 mm or less, more preferably 1000 mm or less, which is fluidized by an air flow, and is preferably 100 mm or less.
As described above, it is preferable that the thickness be 300 mm or more, since the processing amount increases.

It should be noted that the dispersion plate 2 has a pore diameter (0. 0. 1) that substantially allows air to pass through but does not allow granular paste resin to pass through.
A large number of air holes having a hole diameter of 3 to 1 mm (pore diameter: 0.3 mm)
8 to 1.5%). Here, the open area ratio refers to an area ratio of (open area of the open hole / area of the dispersion plate) expressed as a percentage.

Air is blown by the blower 5, heated to a predetermined temperature by the heater 6, and supplied to the bottom of the fluidized-bed container 1 (below the dispersion plate 2). The supplied hot air is
Predetermined superficial velocity (m / s) according to the opening of the air volume control valve 4
As a result, an upward air current flows through the ventilation hole from the lower part of the dispersion plate 2 to contact the granular paste resin fluidized layer 3, and while flowing the layer 3, the monomer emerging from the inside of the granular paste resin Is removed. The hot air containing the monomer is discharged from the upper part of the fluidized bed container 1 through the dust collecting device 7 by the suction blower 8.

The fine particles flying along with the air flow are collected by the dust collector 7 and passed through the rotary valve 9 to form the fluidized bed 3.
Returned.

The superficial superficial velocity is preferably at least 0.05 m / s, more preferably at least 0.1 m / s from the viewpoint of uniformly flowing the powder in the fluidized bed, and is preferably at most 0.5 m / s. And more preferably 0.3 m / s or less from the viewpoint of minimizing the amount of fine powder scattered from the fluidized bed.

After the treatment for a predetermined time, the granular paste resin is sampled, and the residual monomer content in the granular paste resin is measured to determine the residual monomer content.

The granular paste resin from which the residual monomer has been removed is taken out from the resin outlet.

FIG. 2 shows a continuous fluidized bed monomer removing apparatus. Fluidized bed 3 from resin storage tank rotary valve 12
And a batch type fluidized bed monomer removing apparatus shown in FIG. 1 except that it is treated and discharged for an average residence time calculated from the supply amount and the resin amount in the fluidized bed 3. Basically it does not change. Here, the average residence time is calculated by the following equation.

[0040]

(Equation 1)

In FIG. 2, 1 is a fluidized bed container, 2 is a dispersion plate (punched metal), 3 is a fluidized bed of granular paste resin obtained by drying a polymer latex, and h is the thickness of the fluidized bed. , 4 is an air volume adjustment valve, 5 is a blower, 6
Is a heater, 7 is a dust collector, 8 is a suction blower, 9 is a rotary valve, 10 is a resin outlet, 11 is a resin storage tank,
Reference numeral 12 denotes a resin storage rotary valve. R is a supply resin.

When the residual monomer in the granular paste resin is removed by the continuous fluidized bed type monomer removing apparatus shown in FIG. Feed continuously to the layer. At this time, the resin is introduced onto the dispersion plate 2 in the fluidized bed container 1 so as to have a predetermined fluidized bed thickness h. The fluidized bed thickness h is the same as in the case of the batch type fluidized bed type monomer removing apparatus.

The granular paste resin treated for a predetermined time is continuously taken out from the resin outlet 10.

The predetermined time in the continuous type fluidized bed type monomer removing apparatus is the above-mentioned average residence time. Since the granular paste resin has a residence time distribution in the monomer removal treatment in the continuous type fluidized bed type monomer removing device, the residual monomer content is equivalent to that of the batch type fluidized bed type monomer removing device. In order to perform the treatment, it is necessary to perform the treatment for a time two to three times as long as the treatment time in the batch type fluidized bed type monomer removing apparatus.

In a preferred embodiment of the present invention, a polymer latex prepared by subjecting a monomer mixture mainly composed of a vinyl chloride monomer to emulsion polymerization or fine suspension polymerization in an aqueous medium is dried. The obtained granular paste resin having a residual monomer content of several tens of ppm and an average particle diameter of 30 to 100 μm is uniformly contacted with an air stream at 20 to 60 ° C., preferably 30 to 50 ° C. (for example, for 10 to 360 minutes, Is 10 to 200 minutes, in particular 20 to 120 minutes, superficial velocity 0.05 to 0.5 m / s, furthermore 0.1 to 0.3 m
/ S), the residual monomer content becomes 1
It is possible to produce a granular paste resin which is reduced to about 5 ppm and which has no problem in quality such as sol-forming property as the paste resin.

The granular paste resin in which the residual monomer has been reduced in this way may be pulverized and used as a pulverized resin without any particular limitation.

[0047]

EXAMPLES Next, the method of the present invention will be described based on examples and comparative examples, but the present invention is not limited to these examples.

Evaluations in the following Examples and Comparative Examples were performed by the following methods.

(Residual monomer content) 1.5 g of the granular paste resin was dissolved in 50 ml of tetrahydrofuran and measured according to a gas chromatography method, and was measured per 1,000,000 parts (parts by weight, hereinafter the same) of vinyl chloride resin. Number of copies.

(Quality of Granular Paste Resin) Evaluation was made based on the coarse particle size in the sol. That is, 500 g of the granular paste resin and 325 of dioctyl phthalate (DOP)
g with a 5L Hobart mixer (Shinagawa Kogyo Co., Ltd.)
5DMV type) and rotate at 25 ° C with hook hook 141
and stirring at a speed of 67 rpm for 10 minutes.
Produce a sol. JIS determines the size of undispersed material in sol
K 5400 "Coating paint general test method" 4.4 Measure by the method of the test of 4.4, and judge by the A method. That is, pour the sol into the groove of the crush gauge, squeeze it with a scraper, make a layer of sol in the groove so that the thickness continuously changes from 100 μm to 0 μm, The thickness is read to estimate the diameter of the agglomerates in the sol. The measured value of this agglomerate is 30μ
If it was less than m, the quality was evaluated as good (○), and if it exceeded 30 μm, the quality was evaluated as poor (×).

Production Example 1 A spray dryer (tower diameter: 2.75 m) equipped with a rotating disk type atomizer (diameter: 8.4 cm) was prepared by polymerizing a polymer latex of vinyl chloride resin for paste having a solid content of 50% obtained by polymerization. The tower length is 3.0 m for the straight body and 2.2 for the conical part.
m, the conical corner is 60 degrees) at 30 kg / h, and dried and granulated. The air used for drying had an inlet temperature of 90 ° C. and an outlet temperature of 48 ° C., and the rotating speed of the rotating disk was 7000 rpm.

The obtained granular paste resin had an average particle size of 80 μm, an angle of repose of 36 °, and a bulk density of 0.512 g / cc.
And the residual monomer content was 100 ppm.

The basic particle size of the vinyl chloride resin for the paste in the polymer latex was measured with a Coulter counter (TAII, manufactured by Coulter, Inc.).
Two types, 2 μm and 3.2 μm, were produced. These are called samples A and B, respectively.

Examples 1 to 3 Sample A was placed in a batch type fluidized bed type monomer removing apparatus (inner diameter of fluidized bed = 16 cmφ, height = 1200 mm) shown in FIG.
kg (Example 1), 5 kg (Example 2) and 8 kg (Example 3), respectively, and the superficial velocity of the air sent to the fluidized bed vessel,
The treatment temperature was adjusted to 0.2 m / s and 40 ° C. respectively, and the thickness of the fluidized bed was changed as shown in Table 1, and 100 ppm
The processing time required to reduce the residual monomer content to 5 ppm and 1 ppm was determined. The results are shown in Table 1 together with the quality evaluation.

Examples 4 to 6 The thickness of the fluidized bed and the treatment temperature were adjusted to 0.5 m and 40 ° C., respectively, and the superficial velocity was changed as shown in Table 1 to 100
5 ppm and 1 p
The processing time required to reduce to pm was determined. The results are shown in Table 1 together with the quality evaluation.

Example 7 Using Sample B, the processing time was determined under the same conditions as in Example 2. The results are shown in Table 1 together with the quality evaluation.

Examples 8 to 11 Using the sample B, the fluidized bed thickness and the superficial velocity were adjusted to 0.5 m and 0.2 m / s, respectively, and the treatment temperature was changed as shown in Table 1. The processing time required to reduce the monomer content remaining at 100 ppm to 5 ppm and 1 ppm was determined. The results are shown in Table 1 together with the quality evaluation.

Comparative Example 1 Under the same conditions as in Examples 8 to 11, only the treatment temperature was set to 70 ° C.
And the processing time was determined. The results are shown in Table 1 together with the quality evaluation.

Comparative Example 2 Sample B was placed in a paper bag containing 25 kg,
The solution was stored at a temperature of 20 to 25 ° C., and the amount of residual monomer in the resin was measured. The number of days required to reach 5 ppm was as very long as 13 days. The results of the quality evaluation are shown in Table 1 and were satisfactory.

[0060]

[Table 1]

From the results of Examples 1 to 3, it can be seen that the processing time becomes longer as the thickness of the fluidized bed increases. Also, from the results of Examples 4 to 6, it is understood that the processing time can be shortened by increasing the superficial velocity. Furthermore, a comparison between Example 2 and Example 7 shows that the processing time depends on the basic particle diameter in the latex, and that the processing time increases as the basic particle diameter increases. Further, Examples 8 to 11
It can be seen from the result that the processing time becomes shorter as the processing temperature becomes higher. However, the results of Comparative Example 1 show that when the processing temperature reaches 70 ° C., the processing time is significantly shortened, but the quality is deteriorated. On the other hand, from the results of Comparative Example 2, it can be seen that it takes 13 days to reduce the amount of residual monomers in the resin, if it is stored alone, for an extremely long time.

[0062]

According to the present invention, when a granular vinyl chloride paste resin is produced by the method of the present invention, a resin having a low residual monomer content and a good quality can be obtained in a short time.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a batch type fluidized bed type monomer removing apparatus that can be used in the production method of the present invention.

FIG. 2 is an explanatory view showing an example of a continuous fluidized bed type monomer removing apparatus that can be used in the production method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fluidized bed container 2 Dispersion board (punched metal) 3 Granular paste resin fluidized bed obtained by drying polymer latex 4 Air flow control valve 5 Blower blower 6 Heater 7 Dust collector 8 Suction blower 9 Rotary valve 10 Resin take Outlet 11 Resin storage tank 12 Resin storage tank rotary valve h Fluidized bed thickness R Supply resin

Claims (2)

[Claims] 1. A granular vinyl chloride-based paste resin obtained by drying a polymer latex produced from a monomer mixture mainly composed of a vinyl chloride monomer, and
A method for removing residual monomers from a granular vinyl chloride-based paste resin, which is brought into contact with an air stream at 60 ° C. 2. The method for removing residual monomers according to claim 1, wherein the average particle size of the granular vinyl chloride paste resin is in a range of 30 to 100 μm.