KR20000055274A - Method for preparing styrenic resin particles with high degree of expansion using a small amount of blowing agents - Google Patents

Abstract

PURPOSE: A method is provided to manufacture an excellent low-foaming agent and high-foaming styrenic resin particle having an affinity to the environment with the foaming agent of a low content of less than 4% and excellent in anti-lumping effects and heat-stability when a high-foaming is happened. CONSTITUTION: A manufacturing method for a low-foaming agent and high-foaming styrenic resin particle comprises the next followings. A dispersion step dissolves Glyceryl tristearate (GTS) of 0.05 to 1.0 phr and Ethylene vinyl acetate-alcohol copolymer (EVA-Copolymer) of 0.01 to 0.05 phr in styrenic monomer. Tertiary dodecyl mercaptane (TDDM) of 0.05 to 0.5 phr is gradually added until a suspension rate is reached to 30 to 50% of the suspension reactant from a starting point of the reaction. A foaming agent is added at the point of that the suspension rate is 30 to 50%. And Zinc-stearate (Zn-St) of 0.01 to 0.5 phr is added after manufacturing the foaming styrenic resin particle.

Description

METHOD FOR PREPARING STYRENIC RESIN PARTICLES WITH HIGH DEGREE OF EXPANSION USING A SMALL AMOUNT OF BLOWING AGENTS}

The present invention relates to an environment-friendly foaming agent content of 4% or less, and to a method for producing a low-foaming foamed styrene resin particles having excellent anti-lumping effect and excellent thermal stability at high temperature and high pressure foaming, and more specifically, VOC _S ( Low foaming agent and high foaming styrene with excellent thermal stability and almost no limit on product applicability as it has very low content of 3 ~ 4% of foaming agent such as pentane and butane, which is limited as usage. It relates to a method for producing resin particles.

In general, the expandable polystyrene resin is foamed as a representative foaming resin and is widely used as a building material such as insulation, soundproofing material, packaging for agricultural and marine products or home appliances, or disposable containers.

As a method for preparing expandable polystyrene resin particles used for such a purpose, a method of preparing expanded particles by injecting 7% by weight of pentane or butane gas into a blowing agent to 93% by weight of a polystyrene monomer having a low boiling hydrocarbon is usually used. However, pentane or butane gas, which is used as a blowing agent, is restricted to use because it is defined as VOCs, or organic volatile chemicals. For example, when the gas content in the foamed product is 4% or more, an environmental burden is charged separately. There is a need in the art for the development of a method that can improve the foamability while lowering the content of the blowing agent. In addition, the above-mentioned efforts are being made in developed countries such as the United States, which are sensitive to environmental issues, and many technical efforts have been made in developed companies such as BASF and ARCO.

As a technique related to the production of high foaming styrene resin particles with low foaming agent, US Pat. No. 5,112,875 or 5,110,524 describes the production of oligomers in polymers by using a special chain transfer agent for the production of high foaming styrene resin particles. By introducing a method for use as a plasticizer, by obtaining the optimization of the molecular weight distribution through the use of these new materials it is possible to obtain the desired foamability as a low content blowing agent.

However, in the prior art relating to the production of expandable styrene resin particles, in most cases, there is no special mention regarding the content of the blowing agent used in the production of the expandable styrene resin particles, although there is a reference to some content, it is approximately 4 to 8% by weight. It was not a technical proposal for the low content. The reason for this is that low foaming agents have general foaming properties, and thus the foaming properties should be improved through a new technology, and the development of foaming techniques using the above-mentioned chain transfer agent has only recently been made.

Recently, as the environmental problem of VOCs emission is on the rise, the interest in the foaming agent content of the expandable styrene resin is gradually increasing. Therefore, the related technology development is actively progressed. To achieve this, it is necessary to secure physical properties such as high foaming thermal stability and excellent molding cycle time.

An object of the present invention is to solve the conventional problems as described above, development of foaming agent efficiency optimization process applying a new stable suspension polymerization system, the application of foaming aid of glyceryl tristearate, the polymerization rate 30-50% from the start of polymerization Through the combination of incremental addition of TDDM (t-dodecyl mercaptane) until it reaches a maximum of 4% of the foaming agent content while increasing the foamability of the resin particles of the ethylene vinyl acetate-alcohol copolymer The present invention provides a method for producing a low-foaming, highly foamable styrene resin particle having excellent thermal stability with little lumping even at high temperature and high pressure foaming through the use of modified and zinc stearate.

That is, the present invention comprises the steps of dissolving and dispersing 0.05 to 1.0 phr of glyceryl tristearate and 0.01 to 0.5 phr of ethylene vinyl acetate-alcohol copolymer in a styrene monomer to prepare an expandable styrene resin; Incrementally adding 0.05 to 0.5 phr of tertiarydecyl mercaptan from the start of the reaction to the polymerization rate of 30 to 50%; Adding a blowing agent when the polymerization rate reaches 30 to 50%; It is to provide a low-foaming agent high foaming styrene resin particles comprising the step of adding 0.01 to 0.5phr of zinc stearate after the production of foamed styrene resin particles.

1 is a graph showing the time foamability of the expandable styrene resin particles according to the present invention,

2 is a graph showing the lumping effect of the expandable styrene resin particles according to the present invention,

3 is a graph showing the cycle-time of the expandable styrene resin particles according to the present invention.

Hereinafter, the present invention will be described in more detail.

In the present invention, in order to obtain a high foaming property with a low foaming agent, glyceryl tristearate of 0.05 phr to 1.0 phr (hereinafter referred to as the unit phr (parts per hundred parts of styrenic monomer in the present invention) is an incidental to 100 parts of styrene monomer Define as a foaming aid. To this end, by dissolving glyceryl tristearate in the styrene monomer before the polymerization proceeds, the polymerization proceeds to obtain a styrene resin in which glyceryl tristearate is uniformly dispersed, thereby high foamability without deteriorating the thermal stability of the resin. This makes it possible to obtain styrene resin particles. About 3 times the foamability improvement can be obtained per 0.1 phr of glyceryl tristearate, and when it exceeds 1.0 phr, the thermal stability decreases rather than the foamability improvement, which is not preferable.

In order to achieve excellent thermal stability with little lumping during foaming, the present invention dissolves ethylene vinyl acetate-alcohol copolymer in a styrene monomer in the range of 0.01 to 0.5 phr, and then polymerizes the surface of the foamed styrene resin particle by ethylene vinyl acetate-alcohol. The copolymer is converted into copolymer and 0.01 to 0.5 phr of zinc stearate is mixed with the expandable styrene polymer in the form of powder so that excellent thermal stability is achieved in which foaming does not occur between foam particles by steam during foaming.

This effect, which does not cause lumping even under high temperature and high pressure foaming conditions, enables additional foamability improvement in terms of high temperature and high pressure foaming conditions, and can be used for applications requiring higher foamability due to its high commercial applicability. .

The present invention is primarily characterized by excellent foamability, which exhibits up to 100 times the maximum foamability as a low content foaming agent of up to 4% by weight.

To this end, in the present invention, styrene resin particles having an average molecular weight of 150,000 to 200,000 and a PDI (Poly Dispersity Index) of 3 to 4 are used as the basic resin of the expandable resin.

This is because when the styrene resin having a higher molecular weight is used as the base polymer, a foaming agent of 4% by weight or more proposed above is required in order to obtain a high foaming capacity of 100 times the maximum foamability. This is because it is lowered and not easily applied commercially.

In addition, in order to develop a styrene resin having a molecular weight distribution of PDI 3-4 level, TDDM (t-dodecyl mercaptane) is gradually added from the start of polymerization until the polymerization rate is 30 to 50%. When the base polymer having the molecular weight distribution thus prepared is utilized as the foamable resin, the low molecular weight polymer acts as a plasticizer, which is very useful for obtaining high foamability.

The present invention uses a novel stable suspension polymerization method as a further technique for obtaining a high foaming property with a low foaming agent to stably add a blowing agent at a low polymerization rate of 50% or less. In the state where the polymerization rate is further advanced, the addition of the blowing agent is most preferable because the impregnation efficiency (foaming force / foaming agent) is relatively low. In the conventional case, when the blowing agent is in a state in which the polymerization rate is sufficiently advanced to 70% or more, this is because when the blowing agent is added at a low polymerization rate, the surface of the resin particles is softened due to the blowing agent and agglomeration between the resin particles is severely generated. .

However, the present invention applies a novel suspension polymerization method characterized by a combination of a suspension stabilizer consisting of a solid fine powder, an electrolyte, an interfacial adsorptive polymer, and a water-soluble peroxide salt, whereby the growth of particles from the start of the polymerization until the completion of the polymerization is applied. A very stable dispersion system that does not occur is obtained and through this, it is possible to add a blowing agent without aggregation between resin particles even at a low polymerization rate of 50% or less. The addition of blowing agent at low polymerization conversion not only facilitates impregnation of the blowing agent in the beads but also plays a very important role in obtaining high foamability even with a low content of blowing agent.

The present invention uses a volatile organic compound (C _N H _{2 N + 2} ) as the blowing agent, most preferably 4 wt% or less of pentane, and has a maximum foaming property of 100 times that of high foaming and almost no lumping even under high temperature and high pressure foaming conditions. It has excellent thermal stability, and at the time of molding, it has more than 30% faster cycle time than the product with general foaming agent, so it is economical and can be applied to all applications of existing foamed styrene resins such as agricultural and marine product packaging materials, home appliance packaging materials, and insulation materials. have.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Example 1

In the pre-dissolution tank 1, 10 kg of styrene monomer was added, and 50 g of polyethylene wax, 20 g of glyceryl tristearate, and 20 g of ethylene vinyl acetate-alcohol copolymer were added while stirring at 110 rpm. The temperature was raised to 70 ° C. and maintained for 60 minutes. After dissolving the solution, it is allowed to stand at room temperature and cooled.

In the pre-dissolution tank 2, 160 g of benzoyl peroxide and 100 g of t-butylperbenzoate are added to 30 kg of styrene monomer, and dissolved over 30 minutes. The solution made in the preliminary dissolution tank 1 is quenched and stirred for 30 minutes to prepare a dispersion.

Separately, in a 100-l pressure vessel, 40 kg of pure water was added and 150 g of tricalcium phosphate, 60 g of sodium nitrate, 15 g of dodecylbenzenesulfonate, and 8.0 g of magnesium persulfate were added to prepare a suspension. Stir at 110 rpm for minutes. Thereafter, the temperature of the reactor was increased to 90 ° C., and then 120 g of TDDM (t-dedecyl mercaptane) was gradually added until the polymerization rate reached 40%, followed by polymerization. After that, the reactor is sealed and 1500 g of pentane is introduced at a rate of 1 g / min for 90 minutes.

Next, the temperature is raised to 110 ° C. for 70 minutes and maintained at 120 ° C. for 5 hours so that the content of unreacted styrene monomer is up to 1000 ppm or less.

In this case, the introduced blowing agent is impregnated into the glass transition polystyrene resin particles to be made of expandable styrene resin particles.

After cooling to 45 ° C. or less, the residual blowing agent is released. At this time, when the pressure of the reactor drops to normal pressure, it can be discharged to obtain expandable styrene resin particles in a slurry state.

The obtained polymer is separated from water by dehydration, and then dried on a fluidized bed to remove water on the surface of the particles by 0.3% or less, and then sorted by particle size.

Among them, 1 kg of a polymer having a particle size of 0.5 to 1.2 mm is placed in a mixer, and 0.5 g of zinc stearate, 0.5 g of glyceryl monostearate, and 0.5 g of glyceryl tristearate are added, followed by stirring for 30 minutes. Finally, the expandable styrene resin particles are completed.

The molecular weight and the blowing agent (pentane) content of the final product thus obtained were measured using a viscosity tube and gas chromatography (Gas Chromatography), and are shown in Table 2.

In addition, the final product sorted to a particle size of 0.5 ~ 1.2㎜ was measured using a time foamer specially manufactured by Daegong Co., Ltd. to measure the time and maximum foaming properties (usually 9 minutes foaming) is shown in Table 3 and FIG.

In order to measure the foaming and molding properties, after foaming at a magnification of 60 times using a batch foaming machine (model name: HLC-901) specially manufactured by Daegong, foaming properties such as rumping are shown in Table 4 and FIG. The molding properties such as molding cycle-time were measured using a molding machine (model name: DKM 90VS) specially manufactured by Daegong Co., Ltd. and are shown in Table 5 and FIG. 3.

Comparative Example 1

In the same manner as in Example 1, but 120g TDDM (t-dodecyl mercaptane) was added to the reactor after raising the temperature to 90 ℃.

Comparative Example 2

In the same manner as in Example 1, the polymerization was performed without adding 120 g of t-dodecyl mercaptane (TDDM).

Comparative Example 3

10 kg of styrene monomer was added in the pre-dissolution tank 1, and 50 g of polyethylene wax and 20 g of ethylene vinyl acetate-alcohol copolymer were added while stirring at 110 rpm. The temperature was raised to 70 ° C. and maintained for 60 minutes. To cool.

110 g of benzoyl peroxide and 60 g of t-butylperbenzoate were added to 30 kg of styrene monomer in the preliminary dissolution tank 2 and dissolved over 30 minutes. Then, the solution made in the preliminary dissolution tank 1 was quenched and stirred for 30 minutes to prepare a dispersion.

Separately, 40 kg of pure water was added to a 100 L pressure reactor, and the suspension was prepared by adding 150 g of tricalcium phosphate, 60 g of sodium nitrate, 15 g of dodecylbenzenesulfonate, and 8.0 g of magnesium persulfate as a dispersant. Stir at 110 rpm for minutes. Thereafter, the temperature of the reactor is raised to 90 ° C. and maintained until the polymerization rate reaches 75% while maintaining the temperature. Thereafter, the reactor was sealed, and then heated at 110 ° C. for 70 minutes, and 3200 g of pentane was added at a constant amount of 70 minutes at a rate of 1 g / min.

Next, the mixture was maintained at 120 ° C. for 5 hours so that the content of unreacted styrene monomer was less than or equal to 1000 ppm, and the same was carried out in the same manner as in Example 1.

Comparative Example 4

It carried out similarly to Example 1, but changed the benzoyl peroxide content to 110g, and changed the t-butylperbenzoate content to 60g.

Comparative Example 5

The same procedure as in Example 1 was carried out except that ethylene vinyl acetate-alcohol copolymer was not added in preparing the dispersion, and zinc stearate was not added in the mixer after the final polymer was obtained.

Table 1 shows each component used in the preparation of the styrene resin particles of Example 1 and Comparative Examples 1 to 5.

Composition (phr) Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Initiator BPO 0.400 0.400 0.400 0.275 0.275 0.400 TBPB 0.250 0.250 0.250 0.150 0.150 0.250 Conversion time of blowing agent 40% 40% 40% 75% 40% 40% TDDM Incremental Input 0.30 0.30 (batch) - - 0.30 0.30 Foaming Agent (Pentane) 3.75 3.75 3.75 8.00 3.75 3.75 Inner-GTS 0.50 0.50 0.50 - 0.50 0.50 EVA-Copolymer 0.50 0.50 0.50 0.50 0.50 - coating Zn-St 0.05 0.05 0.05 0.05 0.05 - GMS 0.05 0.05 0.05 0.05 0.05 0.05 GTS 0.05 0.05 0.05 0.05 0.05 0.05

1.BPO (Purity 75%): Dibenzoyl peroxide

2. TBPB: t-Butyl perbenzoate

3.Inner-GTS: Glyceryl triacetate used as plasticizer

tristearate)

EVA-Copolymer: Ethylene vinyl

acetate-alcohol copolymer)

5.Zn-St: Zinc-Stearate

6.GMS: Glyceryl monostearate

7. GTS: Glyceryl Tristearate Used as Coating

tristearate)

8.TDDM: t-Dodecyl Mercaptane (Chain Transfer Agent)

Composition (phr) Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Initiator BPO 0.400 0.400 0.400 0.275 0.275 0.400 TBPB 0.250 0.250 0.250 0.150 0.150 0.250 Conversion time of blowing agent 40% 40% 40% 75% 40% 40% TDDM Incremental Input 0.30 0.30 (batch) - - 0.30 0.30 Foaming Agent (Pentane) 3.75 3.75 3.75 8.00 3.75 3.75 Inner-GTS 0.50 0.50 0.50 - 0.50 0.50 EVA-Copolymer 0.50 0.50 0.50 0.50 0.50 - coating Zn-St 0.05 0.05 0.05 0.05 0.05 - GMS 0.05 0.05 0.05 0.05 0.05 0.05 GTS 0.05 0.05 0.05 0.05 0.05 0.05 Chemical analysis Molecular Weight (Mv) 175000 178000 185000 238000 241000 181000 PDI 3.87 2.15 1.89 1.77 3.62 3.79 Pentane (%) 3.51 3.34 3.42 6.23 3.43 3.45 Time foamability 5 minutes 83 76 72 68 69 82 7 minutes 94 83 77 75 77 91 9 minutes (max) 103 88 82 80 83 101

Time-foaming property is a foaming pressure according to steam time (5 minutes, 7 minutes, 9 minutes) at a steam pressure of 0.2kgf / ㎠.

Composition (phr) Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Initiator BPO 0.400 0.400 0.400 0.275 0.275 0.400 TBPB 0.250 0.250 0.250 0.150 0.150 0.250 Conversion time of blowing agent 40% 40% 40% 75% 40% 40% TDDM Incremental Input 0.30 0.30 (batch) - - 0.30 0.30 Foaming Agent (Pentane) 3.75 3.75 3.75 8.00 3.75 3.75 Inner-GTS 0.50 0.50 0.50 - 0.50 0.50 EVA-Copolymer 0.50 0.50 0.50 0.50 0.50 - coating Zn-St 0.05 0.05 0.05 0.05 0.05 - GMS 0.05 0.05 0.05 0.05 0.05 0.05 GTS 0.05 0.05 0.05 0.05 0.05 0.05 Foam property Magnification 60 times 60 times 60 times 60 times 60 times 60 times Cycle-time 40 sec 53 sec 69 sec 43 sec 58 sec 41 sec Lumping 0.04% 0.02% 0.01% 0.01% 0.02% 2.58%

In foaming properties, the cycle-time represents the foaming rate as the time spent foaming at the target magnification (60 times above).

Lumping is a weight ratio of foaming particles which are not lumped and broken between the foaming granules (by heat during foaming) with respect to the initially charged beads, and is commonly used as comparative data of thermal stability.

Furtherance Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Aging 4HR Surface pressure 1.34 1.36 1.38 1.39 1.38 1.34 Vacuum cooling 38 33 30 108 59 36 Molding time 113 108 104 179 132 111 Water content 6.45 6.63 6.78 4.47 6.39 6.74 Welding 90 90 85 90 80 90 Compressive strength 857 849 846 876 878 852 Aging 24HR Surface pressure 1.35 1.37 1.39 1.36 1.39 1.35 Vacuum cooling 40 36 31 99 55 38 Molding time 115 111 105 151 127 113 Water content 6.03 6.11 6.24 5.42 7.13 6.16 Welding 95 95 85 85 80 95 Compressive strength 871 866 867 871 875 873

1. Surface pressure refers to the maximum pressure in the mold when steam is introduced into the mold after foam lip filling is completed (unit kgf / cm 2).

2. Vacuum cooling means vacuum cooling time (unit sec).

3. Molding time is the total molding time from filling to completion of release (unit sec).

4. The moisture content is the weight ratio of the molded part dried at 60 ° C for 24hr to the weight of the molded part immediately after molding (%).

5. Fusion refers to the number of foam particles torn in the unit area relative to the number of 3 cm2 foam granules in horizontal and vertical units when the molded product is broken (unit%).

6. Box compressive strength according to Cheil Industries Analysis Standard Method (unit kgf / ㎠).

As described above, the expandable styrene resin particles prepared according to the present invention have an extremely low blowing agent content of pentane, which is defined as VOC _S (volatile organic chemicals), and thus are environmentally friendly products that are distinguished from ordinary foaming resin particles. In spite of the content, the maximum expansion ratio is 100 times when foaming, so the applicability of the product is superior to that of conventional foaming styrene resin, so that it can replace existing foaming styrene resin, and it has excellent thermal stability and rapid molding cycle time. In addition, it is expected to expand its scope of application in the future.

Claims (4)

In preparing a foamable styrene resin, dissolving and dispersing 0.05 to 1.0 phr of glyceryl tristearate and 0.01 to 0.5 phr of ethylene vinyl acetate-alcohol copolymer in styrene monomer; Incrementally adding 0.05 to 0.5 phr of tertiarydecyl mercaptan from the start of the reaction to the polymerization rate of 30 to 50%; Adding a blowing agent when the polymerization rate reaches 30 to 50%; A method of producing a low foaming agent highly foamable styrene resin particles comprising the step of adding 0.01 to 0.5 phr of zinc stearate after the production of foamable styrene resin particles. The method of producing a low foaming agent highly foamable styrene resin particle according to claim 1, wherein a volatile organic compound (C _N H _{2N + 2} ) is added at less than 4.0% by weight as the blowing agent. The method of claim 5, wherein the volatile organic compound (C _N H _{2 N + 2} ) blowing agent is pentane. The method of claim 1, wherein the expandable styrene particles have an average molecular weight of 150,000 to 200,000 and a PDI (Poly Dispersity Index) of 3 to 4.