KR100497155B1 - Pellet-Type Foams Of Non-crosslinked Polypropylene Resin Having Lower Melting Point - Google Patents

Abstract

The present invention relates to an uncrosslinked pellet-like polypropylene foam having a melting point of 125 ° C to 140 ° C. Since the non-crosslinked pellet-type polypropylene foam of the present invention has a low melting point and a content of 80% or more of closed cells, there is an effect that can be easily formed using such foam.

Description

Pellet-Type Foams Of Non-crosslinked Polypropylene Resin Having Lower Melting Point}

The present invention relates to an uncrosslinked pellet-like polypropylene foam having a melting point of 125 ° C to 140 ° C.

Polypropylene resin foams are widely used as packaging materials, building materials, insulation materials, etc. because of their excellent mechanical strength and cushioning properties. However, since polypropylene exhibits high crystallinity and low melt viscosity and is difficult to crosslink, it is extremely difficult to obtain a highly expanded product from polypropylene.

U.S. Patent 5,527,573 (June 18, 1996) discloses an extruded polypropylene resin foam having a closed cell and several methods of making the same. However, the United States produced by the method disclosed in Patent foam is the minimum cross-sectional area of about 5 x 2.54 cm ² and the board types (plank form) of a minimum thickness of 12.7 mm, from about 5 lbs / ft ³ density. Therefore, this type of foam is difficult to mold into the desired shape. For ease of molding, US Pat. No. 6,051,617 discloses foamed polypropylene resin particles and methods for their preparation. However, the polypropylene blowing agent particles disclosed in this US patent are prepared by grafting a vinyl comonomer onto a polypropylene resin and foaming the modified copolymer resin thus formed. U.S. Patent No. 6,077,875 (June 20, 2000) discloses foamed and fired beads of polypropylene resins prepared from uncrosslinked propylene-ethylene random copolymers. The foam beads produced in this US patent have an open cell content of 40% to most preferably 25% and a melting point of at least 141 ° C.

The non-crosslinked polypropylene resin can be recycled and the pellet-shaped foam prepared therefrom is advantageous in that it is easy to mold, but in the process of producing the pellet-shaped foam by extruding it, most of the cells of the foam become open cells and are not practical. . In order for the foam to be practical, it must have mechanical strength by including a closed dell in a significant proportion. In fact, the only company that successfully manufactures and commercializes pelletized foams from non-crosslinked polypropylene resins is Japan's only JSP Corporation. However, the non-crosslinked pellet-type polypropylene foam has a low melting point, which is easy to mold and has excellent reproducibility, and its value is very high. No cases have been reported.

Accordingly, an object of the present invention is to prepare a non-crosslinked polypropylene resin to ensure reproducibility, to form a high content of closed cells to give a satisfactory mechanical strength, melting point so that it can be easily molded into various types of packaging materials, etc. The present invention provides a pelletized polypropylene resin foam having a temperature of 140 ° C. or less and a method of manufacturing the same. We set a number of temperature zones that are specifically varied in a tandem extruder to flow an uncrosslinked polypropylene resin melt having a melting point of 138 ° C. to 140 ° C. along the temperature zone and through this temperature zone. A polypropylene resin melt is mechanically homogenized at a low temperature of 120 ° C to 130 ° C, the molten homogenate thus formed is ignited through a plurality of holes set in the die under pressure, and the foam formed by firing through the hole of the die is cut. This successfully produced uncrosslinked pellet-like polypropylene foam having a closed cell of at least about 80% and a melting point of 125 ° C to 140 ° C.

In one aspect, the present invention provides a non-crosslinked pelletized polypropylene foam having a melting point of 125 ° C to 140 ° C.

As another aspect, the present invention (a) the primary extruder in the first temperature zone of 147 ° C to 153 ° C, the second temperature zone of 167 ° C to 172 ° C, the third temperature zone of 168 ° C to 172 ° C, 218 ° C to A fourth temperature zone of 225 ° C., a fifth temperature zone of 197 ° C. to 203 ° C., and a sixth temperature zone of 188 ° C. to 193 ° C. are set, and the first temperature zone of 167 ° C. to 173 ° C., 147 ° C. to the second extruder. A second temperature zone of 152 ° C, a third temperature zone of 142 ° C to 147 ° C, a fourth temperature zone of 137 ° C to 141 ° C, a fifth temperature zone of 137 ° C to 142 ° C and a sixth temperature of 132 ° C to 137 ° C A non-crosslinked propylene random copolymer having a melting point of 138 ° C. to 140 ° C. was extruded in a tandem extruder having a zone set and a temperature of 248 ° C. to 255 ° C. in a guide connecting the primary extruder and the secondary extruder, ) The formed extrudate is forcedly flowed by pumping at a temperature of 125 ° C to 140 ° C, and (c) the extrudate is brought to a temperature of 120 ° C to 130 ° C Homogenizing, (d) igniting the homogenate through a die, and (e) cutting the ignition to obtain pelleted foams, wherein the non-crosslinked pellets have a melting point of 125 ° C to 140 ° C. Provided is a method for producing a type polypropylene foam.

In another aspect, the present invention provides an apparatus for producing non-crosslinked pelletized polypropylene foam having a melting point of 125 ° C to 140 ° C.

In another aspect, the present invention provides foams molded from uncrosslinked pelletized polypropylene foams having a melting point of 125 ° C to 140 ° C.

Prior to the present invention, it was not possible to produce pelletized foams having a melting point of 140 ° C. or lower. Since pure polypropylene with a melting point of 138 ° C. cures rapidly at temperatures below that, processing at temperatures below 138 ° C. is not possible, thus producing uncrosslinked polypropylene pellet-like foams having a melting point of up to 140 ° C. Of course it has been considered impossible.

However, the present invention has developed uncrosslinked polypropylene pellet-like foams having a low melting point temperature of 140 ° C. or less and an open cell content of about 20% or less. This development has been made possible by the application of a combination of several discoveries. For example, the present inventors are based on the tandem extrusion method, by specifically setting the temperature conditions during the first extrusion and the second extrusion, and specifically homogenizing the melt produced from the extruder at a low temperature of 125 to 130 ° C. It has been found that the open cell content of the foam is significantly reduced. In addition, the inventors have discovered that at least about 80% of closed cells are formed only within a certain temperature range until the non-crosslinked polypropylene resin having a melting point of 138 ° C to 140 ° C is extruded and then fired. In addition, the inventors have found that from a non-crosslinked polypropylene resin having a melting point of 138 ° C. to 140 ° C., the melting point of foams produced according to the specific processing conditions of the present invention can be lowered to 138 ° C. or less.

Hereinafter, a method of manufacturing the non-crosslinked pellet-type polypropylene foam of the present invention will be described in detail for each process. The production process of the present invention consists of extrusion, pumping, homogenization, firing and pelletizing processes.

(1) extrusion

The extrusion process according to the invention can be carried out by modifying it on the basis of a tandem extruder used or known in the art for producing foams. Materials used to prepare non-crosslinked pelletized polypropylene foams according to the invention are uncrosslinked propylene random copolymers having a melting point of 138 ° C. to 140 ° C., nucleating agents, blowing agents and, if necessary, other additives.

The base resin used in the present invention is an uncrosslinked propylene random copolymer having a melting point of 138 ° C to 140 ° C. Examples of other comonomers copolymerized with propylene include ethylene, 1-butene, 1-pentene and 1-hexene. The propylene random copolymer can be a bipolymer such as a propylene-ethylene random copolymer or a propylene-butene random copolymer or a terpolymer such as a propylene-ethylene-butene copolymer. The proportion of comonomer components other than propylene in the copolymer is preferably from 0.05 to 10% by weight.

The nucleating agent serves to disperse the blowing agent and to control the cell size of the foam. Nucleating agents that can be used in the present invention include, but are not limited to, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, ammonium bicarbonate or ammonium carbonate. Preferred is sodium bicarbonate. The larger the amount of nucleating agent used, the smaller the cell of the foam, and conversely, the smaller the amount of the nucleating agent used, the larger the cell of the foam. In the present invention, 0.1% to 0.4% is generally used based on the weight of the resin. If the amount exceeds 0.4%, insufficient dispersion or agglomeration may occur and as a result the cell grows beyond the desired size. In contrast, when the amount is used less than 0.1%, the nucleation action is too weak to reduce the diameter of the cell.

Foaming agents usable in the present invention are generally organic or inorganic blowing agents. Examples of organic blowing agents include aliphatic hydrocarbons such as propane, butane, hexane and heptane, cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane and chlorofluoromethane, trifluoromethane, 1,1-difluoroethane, 1,2 Halogenated hydrocarbons such as 2,2-tetrafluoroethane, methyl chloride, ethyl chloride and methylene chloride. In addition, organic blowing agents that can be used include dichlorotetrafluoroethane, trichlorotrifluoroethane, trichloromonofluoromethane, dichlorodifluoromethane, dichloromonofluoromethane, dibromotetrafluoroethane and the like. do. These fluoro-chlorinated hydrocarbons are preferred in view of foaming workability, non-toxicity and flame retardancy. These organic foams can be used alone or in combination of two or more. Examples of inorganic blowing agents include nitrogen, carbon dioxide, argon and air. These inorganic blowing agents may also be used alone or in combination of two or more. In addition, the organic blowing agent and the inorganic blowing agent may be used by mixing two or more at random. Among the blowing agents mentioned above, inorganic blowing agents are preferred because they do not destroy the ozone layer and are inexpensive. The amount of blowing agent used depends on the expansion ratio of the foam pellet to be obtained, the resin used and the type of blowing agent. The amount of blowing agent used in the present invention is 20% to 30% based on the weight of the resin.

Many other types of additives may be used. Examples of such additives include antioxidants, ultraviolet absorbers, flame retardants, pigments, dyes, metal deactivators, and the like. These additives may be used at 0.1% to 0.3% based on the weight of the copolymer resin. Paraffin wax is used as one preferred embodiment of the present invention. This helps the flow of the copolymer resin and also acts as an antistatic agent to dissipate the static electricity of the copolymer resin. The amount of paraffin wax used is about 0.1% by weight.

The raw material used in the present invention is extruded through a tandem extruder set the characteristic physical conditions of the present invention will be described as follows. The tandem extruder consists of a primary extruder, a secondary extruder and a guide connecting them. The screw compression ratio is usually 3: 1. The inner diameter of the primary extruder cylinder is usually about 60 to 70 mm. The inner diameter of the secondary extruder cylinder is usually about 90 to 95 mm.

The primary extruder is divided into six zones depending on the temperature and each zone corresponds to about 300 to 400 LD. The six zones include a first temperature zone of 148 ° C to 153 ° C, a second temperature zone of 167 ° C to 172 ° C, a third temperature zone of 167 ° C to 172 ° C, a fourth temperature zone of 218 ° C to 223 ° C, and 197 ° C. 5th temperature zone of -203 degreeC, and 6th temperature zone of 188 degreeC-193 degreeC.

The uncrosslinked propylene random copolymer resin and the nucleating agent are melted by flowing into the first zone at a predetermined speed which is set at a temperature of 148 ° C to 153 ° C in advance through a hopper. The inflow rate can be controlled by the rotational speed of the screw and is generally about 20 to 30 rpm, which rotational speed determines the inflow rate of the raw material and the flow rate of the melt. In this case, the inflow rate of the resin usually corresponds to about 25 kg / h. The copolymer resin and the nucleating agent may be introduced at the same time through one hopper, but preferably each is introduced independently through a separate hopper. The second and third temperature zones are maintained at a temperature of 167 ° C. to 172 ° C. and other additives, such as paraffin wax, are introduced at the starting point of the third temperature zone. In the case of paraffin wax, it is melted before pumping and pumped. The fourth temperature zone is also set at 218 ° C. to 223 ° C. at which its blowing agent is introduced by pumping. The melt passing through the fourth temperature zone flows through the fifth temperature zone set at a temperature of 218 ° C to 223 ° C and into a sixth temperature zone set at a temperature of 188 ° C to 193 ° C, respectively.

The melt passing through the sixth temperature zone of the primary extruder is introduced into the secondary extruder through a guide connecting the primary extruder and the secondary extruder. At this time the guide is set to a temperature of 248 ℃ to 153 ℃ and LD is 300 to 400 mm.

Secondary extruders are also divided into six zones depending on the specifically set temperature, each zone corresponding to 470 to 520 mm. The six zones include a first temperature zone of 168 ° C to 173 ° C, a second temperature zone of 147 ° C to 152 ° C, a third temperature zone of 143 ° C to 147 ° C, a fourth temperature zone of 137 ° C to 142 ° C, and 137 ° C. To a fifth temperature zone of 142 ° C and a sixth temperature zone of 132 ° C to 137 ° C. The screw speed of the secondary extruder is generally 8 to 12 rpm.

Each zone set in the primary extruder and the secondary extruder can maintain a particular temperature set by any of the known water cooled, oil cooled or air cooled systems. Among them, water-cooling that adjusts the temperature by the pressure of water is preferable. For example, the cooling water body installed on the cylinder main surface of the extruder can be formed into a hollow shape, and at the same time, the cooling water passage that is open to the inner surface is integrally formed so that the cooling water directly contacts the surface of the cylinder. Can be.

(2) pump

The sixth temperature zone of the secondary extruder may correspond to a flange for connection with the grinding means of the melt according to the process of the present invention, which flange is specifically maintained at 132 ° C. to 137 ° C. by the present invention. Since the temperature is lower than the melting point of 138 ° C of the polypropylene resin, the flow rate of the melt can be considerably lowered. In order to smooth the flow of the melt it is necessary to flow forcibly. This forced flow can be achieved by a gear pump. The temperature at this time is maintained at a temperature of 125 ° C to 140 ° C by water cooling.

(3) homogenization

According to the invention the melt conveyed from the extruder by pumping under a temperature of 125 ° C. to 140 ° C. is homogenized under a temperature of 120 ° C. to 130 ° C. Here, homogenization refers to cutting and simultaneously grinding the melt in the same manner as metstone. In addition, the homogenization allows the melt to have a constant internal and external temperature as a whole. Maintaining the temperature at 120 ° C to 130 ° C in the homogenization process is preferably water-cooled or oil-cooled, more preferably oil-cooled. At this time, the pressure inside the cylinder is about 120kgf / cm ² It reaches a degree.

(4) fire

The homogenized melt is ignited through the dice. Pressure of the cylinder inside the homogenization of the melt formed as described above is such that since the month to 120kgf / cm ^2, by installing a pressure device for maintaining the die pressure from 0.3 to 0.7kgf / cm ^2. Polypropylene resin is ignited through the hole of the die, the hole diameter is usually 0.5 mm to 1 mm and the expansion ratio is usually 5 times the diameter of the microspheres.

(5) pelletization

The foam formed by ignition from the hole of the die is cut out by the cutter at the same time as it flows out of the hole to produce a foam in the form of pellets.

Apparatus of the invention for producing non-crosslinked pelletized polypropylene foam having a melting point of 125 ° C. to 140 ° C. according to the invention, a primary extruder, a secondary extruder connected to a primary extruder, a pumping part connected to a secondary extruder, pumping A homogenization part connected to the part and a die part connected to the homogenization part.

The primary extruder includes a cylindrical cylinder with a rotatable feed screw, a drive unit installed at one end of the cylinder to rotate the feed screw, and a plurality of cooling means and heating means mounted on the outer circumferential surface of the cylinder, and one end of the cylinder corresponding to the drive unit. There is an inlet for injecting polypropylene and a nucleating agent into the cylinder, and an outlet is formed at the other end, and an inlet for injecting additives and foaming agents such as an antistatic agent at an appropriate intermediate point of the cylinder. It is. The polypropylene and the nucleating agent introduced into the cylinder through the inlet are melted and forcedly transferred to the outlet by a feed screw rotating by the driving unit.

The secondary extruder connected to the primary extruder by a guide includes a plurality of cooling means mounted on the cylinder and the outer circumferential surface of the cylinder in which the polypropylene melt discharged from the cylinder of the primary extruder flows through the guide, and controlling the melt temperature inside the cylinder; Heating means.

The pumping part for forcibly transferring the polypropylene melt discharged from the secondary extruder to the next process is rotatable in a state in which the inner space into which the polypropylene melt discharged from the cylinder of the secondary extruder flows is introduced, and interlocked with each other in the casing inner space. It consists of two gears and a drive unit for rotating the gears.

Homogenizer is a rotatably installed cylindrical first housing into which the polypropylene melt flowing from the cylinder of the pumping unit flows, a drive unit for rotating the first housing, a screw connected to the discharge end of the first housing, a second positioned at the outer circumference of the screw And a frame mounted to have a sealed space between the housing and the second housing. A spiral space portion is formed between the screw and the second housing over the entire length of the screw so that the polypropylene melt discharged from the first housing moves along the space portion between the screw and the second housing and is discharged to the portion. In the space formed between the frames, the heat medium oil flows in and flows to control the temperature of the polypropylene melt moving inside the second housing.

The homogenizer is characterized in that it comprises homogenization means for homogeneously crushing the melt of polypropylene. The homogenizing means consists of a rotating plate rotatably installed and a fixed plate installed in close contact with the rotating plate, and the rotating plate includes a plurality of incisions disposed radially, and the fixed plate has a plurality of circular openings. . The introduced polypropylene melt is cut by the edges of each incision in the course of reaching the rotating rotating plate and passing through each cut formed in the rotating plate, and then rotating by the rotating plate rotating between the rotating plate and the fixed plate. Grinding

In the die portion, the polypropylene melt discharged from the homogenizing portion flows in, and is composed of a discharge portion, a cutting portion, and a driving portion to cut the fired foam to a predetermined standard.

In the present invention, each cooling means mounted to the cylinders of the primary extruder and the secondary extruder is a closed casing in which externally supplied cooling water flows in the inner space, and the cooling water supplied into the casing is applied to the surface of the cylinder along the casing. The temperature of the polypropylene melt that flows in contact and moves inside the cylinder is lowered, and each heating means mounted between the two casings uses a heater with a built-in heating wire.

The cylinder of the primary extruder is divided into six temperature zones according to the temperature conditions of the polypropylene melt injected therein, and each temperature zone is controlled by cooling means and heating means mounted on the outer peripheral surface of the cylinder, and the polypropylene melt In the first temperature zone is 147 to 153 ° C, the second temperature zone is 167 ° C to 172 ° C, the third temperature zone is 168 ° C to 172 ° C, and the fourth temperature zone is 218 ° C to 225 ° C and the fifth temperature zone. In 197 degreeC-203 degreeC, and 188 degreeC-193 degreeC is maintained in a 6th temperature zone.

The cylinder of the secondary extruder is also divided into six temperature zones according to the temperature conditions of the polypropylene melt flowing therein, and each temperature zone is controlled by cooling means and heating means mounted on the outer circumference of the cylinder, and polypropylene The melt temperature is 167 ° C to 173 ° C in the first temperature zone, 147 ° C to 152 ° C in the second temperature zone, 142 ° C to 147 ° C in the third temperature zone, 137 ° C to 141 ° C in the fourth temperature zone, and the fifth 137 ° C-142 ° C in the temperature zone and 132 ° C-137 ° C in the sixth temperature zone.

The inside of the guide connecting the primary extruder and the secondary extruder maintains a temperature of 248 ° C to 255 ° C.

The two gears mounted in the casing inner space of the pumping portion rotate in opposite directions toward the center of the inner space to force the polypropylene melt to be transferred to the next process position. In addition, the first housing of the homogenizer is rotatably supported by the support plate through a plurality of bearing blocks, and the driving sprocket of the drive unit is connected to the driven sprocket fixed to the outer circumferential surface of the first housing, so that the first housing is operated according to the operation of the drive unit. It rotates.

The discharge part of the die part consists of a hollow guide bar and a cylinder located outside the guide bar, and a plurality of cavities are formed in the longitudinal direction of the guide bar on the outer circumferential part of the guide bar, so that the polypropylene melt discharged from the homogenizing part is introduced into each cavity. And a plurality of through holes are formed in the portion of the cylinder corresponding to each cavity.

The cutting part includes a support plate positioned at the rear of the discharge part and a cutting member positioned to be movable outside the cylinder in a state of being fixed to the support plate, wherein the cutting member has a plurality of through holes formed at positions corresponding to the respective through holes of the cylinder. The driving unit includes a eccentric cam that rotates by a motor, a crank that rotates in contact with the eccentric cam, and a crank which is connected to the crank to convert the rotational motion of the crank into a linear motion, and then transfer the power switching transmission means to the supporting plate to which the cutting member is fixed. Including, the cutting member is reciprocated along the outer circumferential surface of the cylinder in accordance with the operation of the drive unit to cut the foam ignited through each through hole of the cylinder by the through hole of the cutting member.

Meanwhile, a plurality of grooves are formed at a predetermined position of the cylinder in the longitudinal direction, and in each groove, reciprocating rods each of which can be moved along the groove and one end of which is fixed to the supporting plate are positioned, and the cutting member is fixed by a fixing means. The cutting member is reciprocated on the outer circumferential surface of the cylinder by the reciprocating rod fixed to each reciprocating rod and reciprocating along each groove of the cylinder.

Hereinafter, the detailed configuration and operation of the pellet-type foam manufacturing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a general configuration of the pellet-type foam manufacturing apparatus according to the present invention, the foam manufacturing apparatus according to the present invention is largely connected to the primary extruder 100 by the primary extruder 100, guide 150 Extruder 200, the pumping unit 300 connected to the secondary extruder 200, the homogenizer 400 connected to the pumping unit 300 and the foam mixture discharged from the homogenizer 400 to form a pellet-shaped foam The die part 500 is comprised.

Hereinafter, each of the above-described parts will be described separately.

A. Primary Extruder (100)

FIG. 2 is a plan view showing a cylinder of the primary extruder 100 shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line A-A of FIG. 2, showing the configuration of the primary extruder 100. The primary extruder 100 has a cylindrical cylinder 101 of a predetermined length, a drive unit 102 installed at one end of the cylinder 101, a feed screw 103 rotated by the drive unit 102 in a state in which the cylinder 101 is embedded. And cooling means 104 and heating means 105 mounted on the outer circumferential surface of the cylinder 101.

At one end of the cylinder 101 and the corresponding cylinder 101, inlets 101a and 101b for injecting the raw material polypropylene and the nucleating agent (eg, sodium bicarbonate) into the cylinder 101, respectively; Only the inlet 101a is shown), and the other end is formed with an outlet 101c. In addition, the central portion of the cylinder 101 has an antistatic agent (for example, paraffin wax) input port (101d) and the blowing agent (for example, LPG or CO ₂₎ input port (101e) are formed, respectively.

On the other hand, the cylinder 101 is divided into six temperature zones according to the temperature conditions that the polypropylene melt injected therein, cooling means for controlling the temperature of the polypropylene melt on the outer peripheral surface of the cylinder 101 corresponding to each zone 104 and heating means 105 are mounted.

FIG. 2 is a plan view showing the cooling means 104 and the heating means 105 mounted on the outer peripheral surface of the cylinder 101 of the primary extruder 100 shown in FIG. 1, which will be described with reference to FIG. 3.

The cooling means 104 mounted around the outer circumferential surface of the cylinder 101 corresponding to each of the above-mentioned regions is a closed casing in which cooling water supplied from the outside flows, and its cross section is in a donut shape. The coolant supplied into the casing 104 flows along the casing 104 in contact with the surface of the cylinder 101, thereby lowering the temperature of the inside of the cylinder 101, ie, the moving polypropylene melt. .

The heating means 105 mounted between the two casings 104 is a heater with a built-in heating wire, which raises the temperature of the polypropylene melt lowered by the cooling means 104 to a predetermined temperature.

The function of the primary extruder 100 having the above configuration will be described with reference to each drawing. After operating the driving unit 102, the polypropylene and the nucleating agent are introduced into the cylinder 101 through the inlets 101a and 101b, respectively. According to the operation of the driving unit 102, the feed screw 103 is rotated in the cylinder 101 (of course, the rotational speed of the driving unit is significantly lower than the rotational speed of the driving unit). The polypropylene and nucleating agent are forcibly conveyed towards the other end of the cylinder 101 while melt mixing.

In this process, the antistatic agent and the blowing agent are introduced into the cylinder 101 through the other inlets 101d and 101e formed at the center of the cylinder 101, respectively, and mixed with the melt of the polypropylene.

As described above, the cylinder 101 of the primary extruder 100 is divided into six temperature zones Z1 to Z6 as shown in FIG. 2 according to the temperature conditions of the polypropylene melt moving therein, The length of each temperature zone Z1 to Z6 is about 300 to 400 mm. In a preferred embodiment, the inner diameter of the cylinder 101 is 65 mm and therefore the LD is about 358 mm and the temperature and other conditions of the polypropylene melt according to the respective zones Z1 to Z6 in the cylinder are as follows.

1) First temperature zone Z1: A zone in which polypropylene and a nucleating agent are introduced, the temperature of which is 150 ° C, and the length at which this temperature is maintained, that is, the length of the first temperature zone Z1 is 360 mm.

2) 2nd temperature zone Z2: The polypropylene melt which moves the 2nd temperature zone Z2 maintains the temperature of 170 degreeC.

3) Third temperature zone Z3: The temperature of the polypropylene melt moving through the third temperature zone Z3 maintains the same temperature of 170 ° C as the second temperature zone Z2, and the third temperature zone Z2 Paraffin wax is added to the antistatic agent.

4) fourth temperature zone (Z4): the polypropylene melt maintains a temperature of about 220 ° C. in the fourth temperature zone (Z4), and the blowing agent CO ₂ or LPG in the fourth temperature zone (Z4) cylinder 101 Is put into.

5) The temperature of the polypropylene melt in the fifth temperature zone Z5 is maintained at 200 ° C, and the temperature of the polypropylene melt is maintained at 190 ° C in the sixth temperature zone Z6.

In order to adjust the temperature of the melt of the polypropylene in each of the temperature zones Z1 to Z6 as described above, the cooling means 104 and the heating means 105 mounted in each temperature zone are appropriately operated. That is, by controlling the amount and temperature of the cooling water supplied into the casing, which is the cooling means 104, the current and the application time applied to the heating wire constituting the heating means 105, the polypropylene melt in each region Z1 to Z6. The temperature is adjusted to the above conditions.

On the other hand, when using CO ₂ as the blowing agent to be injected into the cylinder 101 of the primary extruder 100, a CO ₂ supply device is used, the CO ₂ supply device used in the present invention is as follows.

Figure 4 is a view which schematically showing the configuration of the CO ₂ supply, CO ₂ supply device 110 includes a CO ₂ storage tank (110A), evaporated and freeze screen unit (110B), CO ₂ supply unit (110C), It is composed of a CO ₂ stabilization unit (110D) and a storage unit (110E). Stored in a CO ₂ storage tank (110A) CO ₂ is supplied to the gasification furnace and the freezing screen unit (110B) is converted to a vapor form. That is, the CO ₂ is vaporized and vaporized in the course of passing through the freezer in the vaporization and refrigeration unit (110B), and then supplied to the CO ₂ stabilization unit (110D) by a pump which is a CO ₂ supply unit (110C). In the CO ₂ stabilization unit 110D, CO ₂ in vapor form is converted to gas form, and CO ₂ in gas form is stored in the storage unit 110E. The CO ₂ stored in the storage unit 110E is supplied into the first cylinder 101 of the primary extruder 100 described above when the process starts.

The polypropylene melt transferred to the end of the cylinder 101 (moved by the feed screw 103) in accordance with the conditions in each of the temperature zones Z1 to Z6 is passed through the guide 150 to the secondary extruder 200. Flows into. The polypropylene melt passing through the guide 150 maintains a temperature of 250 ° C.

B. Second Extruder (200)

The configuration of the secondary extruder 200 into which the polypropylene melt flows through the guide 150 is the same as that of the primary extruder 100 described above. That is, the cylinder 201 constituting the secondary extruder 200 is also divided into six temperature zones according to the temperature conditions of the polypropylene melt flowing therein, and the outer peripheral surface of the cylinder 201 corresponding to each zone Equipped with cooling and heating means for temperature control of the propylene melt. The configuration of the cooling means and the heating means is the same as the cooling means 104 and the heating means 105 mounted on the outer circumferential surface of the cylinder 101 of the primary extruder 100 shown in FIG. 3, and thus description thereof will be omitted. do.

The cylinder 201 of the secondary extruder 200 is divided into six temperature zones according to the temperature conditions of the polypropylene melt moving therein, and the length of each zone is about 470 to 520 mm. In a preferred embodiment, the inner diameter of the cylinder 101 is 90 mm and therefore the LD is 495 mm and the temperature conditions of the polypropylene melt according to each temperature zone in the cylinder 201 are as follows.

1) 1st temperature zone (inflow part): 170 degreeC

2) 2nd temperature zone: 150 degreeC

3) Third temperature zone: 145 ° C

4) Fourth and fifth temperature zones: 140 ° C.

5) 6th temperature zone (discharge part): 135 degreeC

C. Pumping unit 300

The polypropylene melt discharged at a temperature of 135 ° C. from the secondary extruder 200 flows into the pumping part 300. The melting point of the polypropylene is 138 ° C., so the polypropylene melt discharged from the secondary extruder 200 is in a state where its flow rate is considerably lowered. The pumping unit 300 is used in the present invention in order to forcibly transfer the polypropylene melt to a subsequent process step.

FIG. 5 is a cross-sectional view illustrating an internal structure of the pumping unit 300 and the homogenizer 400 shown in FIG. 1, the left side of which includes an internal structure of the pumping unit 300, and the right side of an internal structure of the homogenizing unit 400. Respectively.

The pumping part 300 into which the polypropylene melt discharged from the cylinder 201 of the secondary extruder 200 flows is rotatably coupled to each other in the casing 301 and the casing 301 inner space having a space formed therein. Two gears 302A, 302B installed and a drive 303 for rotating the gears 302A, 302B. The inlet of the casing 301 is connected to the cylinder 201 and the flange 304 of the secondary extruder 200.

The polypropylene melt discharged from the cylinder 201 of the secondary extruder 200 is introduced into the inner space through the inlet of the casing 301, and then rotates in two opposite directions toward the center of the space. 302B) is forcibly discharged to the discharge portion. That is, the polypropylene melt discharged from the cylinder 201 of the secondary extruder 200 has a temperature of 135 ° C., and the fluidity of the mixture is markedly inferior. Therefore, the pumping unit 300 serves to forcibly flow the polypropylene melt to the next process position.

D. Homogenizer 400

The homogenizing part 400 connected to the discharge part of the casing 301 of the pumping part 300 is divided into a rotating part 400A and a crushing part 400B. The rotating part 400A includes a hollow cylindrical first housing 401, a driven sprocket 402 fixed to the outer circumferential surface of the first housing 401, and a driving part 404 to which the driving sprocket 403 is fixed.

The first housing 401 is rotatably supported by the support plates 407 and 408 via a plurality of bearing blocks 405 and 406. The drive sprocket 403 of the drive unit 404 is connected to the driven sprocket 402 fixed to the outer circumferential surface of the first housing 401, so that the first housing 401 rotates according to the operation of the drive unit 404. do. One end of the first housing 401 corresponds to the discharge end of the casing 301 of the pumping part 300, so that the polypropylene melt introduced from the pumping part 300 flows into the first housing 401. The polypropylene melt in the first housing 401 varies in temperature depending on its location (i.e., the central and outer portions of the inner space of the first housing), so as the first housing 401 rotates, The temperature is kept constant throughout the mixture. At this time, since the new polypropylene melt is continuously forced by the pumping unit 300, the polypropylene melt is transferred at the same time as the rotation.

The crushing unit 400B includes a screw 410 connected to the discharge end of the first housing 401 of the rotating unit 400A, a second housing 411 and a second housing 411 positioned at an outer circumference of the screw 410. It consists of a frame 412 mounted to have a predetermined closed space therebetween. The screw 410 is a configuration in which a spiral having a predetermined depth is formed on an outer circumferential surface of the cylindrical member, and a spiral space portion is formed over the entire length of the screw 410 between the screw 410 and the second housing 411. Accordingly, the polypropylene melt discharged from the high pressure first housing 401 of the rotating part 400A moves along the helical space between the screw 410 and the second housing 411 and is discharged out of the crushing part 400B.

On the other hand, the heat medium oil flows in the space formed between the second housing 411 and the frame 412. That is, one side of the frame 412 is formed with an inlet port 412A through which the heat medium oil flows, and a discharge port 412B through which the heat medium oil is discharged. The heat medium oil introduced into the space between the frame 412 and the second housing 411 through the inlet port 412A is in direct contact with the surface of the second housing 411 to move the temperature of the polypropylene melt moving therein. Adjust The heat medium oil, which flows into the space between the second housing 411 and the frame 412 and serves to control the temperature of the polypropylene melt, is discharged to the outside through the discharge port 412B. Inflow, temperature regulation and discharge proceed continuously, so that the temperature of the polypropylene melt moving in the spiral space between the second housing 411 and the screw 410 is regulated to the set temperature.

At the rear end of the homogenizer 400, that is, at the outlet of the second housing 411, a homogenization means 450 is mounted to crush and homogenize the discharged mixture of polypropylene and the nucleating agent.

6A and 6B are front views of the rotating plate 451 and the fixing plate 452 constituting the homogenizing means 450. The rotating plate 451 and the fixed plate 452 are of the same shape and are mounted in close contact with each other, but the rotating plate 451 is rotatably mounted.

The rotary plate 451 is configured with a plurality of radially cut portions 451A, and each cut portion 451A is configured to be inclined with respect to the center of the rotary plate 451. In addition, a plurality of circular openings 452A are formed in the fixing plate 452.

The edges of each cutout 451A in the process of passing through the cutouts 451A formed on the rotating plate 451A by reaching the rotating plate 451A that rotates the polypropylene melt discharged from the second cylinder 411. edge), so that all polypropylene melts are homogeneously crushed. The crushed polypropylene melt is ground by the rotating plate 451 rotating between the rotating plate 451 and the fixed plate 452 and then discharged through the opening 452A of the fixed plate 452.

E. Dies 500

In this way, the polypropylene melt discharged from the homogenization part 400 in a state where the temperature is controlled is introduced into the die part 500 to be manufactured as a pellet-type foam.

FIG. 7 is a plan view illustrating the structure of the die part 500 illustrated in FIG. 1, FIG. 8 is a cross-sectional view taken along the line BB of FIG. 7, and FIG. 9 is a cutaway view along the line CC of FIG. 8. As a cross-sectional view, the die part 500 is largely divided into the discharge part 500A, the cut part 500B, and the drive part 500C.

The discharge part 500A includes a hollow cylindrical guide bar 501 and a cylinder 502 located outside the guide bar 501. On the outer circumferential portion of the guide bar 501, a plurality of cavities 501A are formed in the longitudinal direction of the guide bar 501, and the polypropylene melt discharged from the homogenizer 400 flows into and flows into each cavity 501A. . A plurality of through holes 502A are formed in the portion of the cylinder 502 corresponding to each cavity 501A.

The cut part 500B consists of the support plate 506 located behind the discharge part 500A, and the cutting member 503 fixed to the support plate 506. As shown in FIG. The cutting member 503 is positioned to be movable outside the cylinder 502, and a plurality of through holes 503A are positioned at positions corresponding to the respective through holes 502A of the cylinder 502, as shown in FIG. Formed. As shown in each drawing, the diameter of the through hole 502A formed in the cylinder 502 is made smaller than the diameter of the through hole 503A formed in the cutting member 503. In the initial position, the through hole 502A of the cylinder 502 corresponding to the center of the through hole 503A formed in the cutting member 503 is located.

On the other hand, a plurality of grooves 502B are formed in the longitudinal direction of the cylinder 502, and the reciprocating rods 505 are located in the grooves 502B, respectively. The cutting member 503 is fixed to each reciprocating rod 505 by fixing means such as bolts, and thus the cutting member 503 is reciprocated by the reciprocating rod 505 reciprocating along each groove 502B of the cylinder 502. 503 is reciprocated on the outer peripheral surface of the cylinder (502).

The driving part 500C of the die part 500 is connected to the eccentric cam 511 rotating by the motor 510, the crank 512 rotating in contact with the eccentric cam 511, and the crank 512, and the crank 512. And a power change transmission means 513 for converting the rotational motion of the linear motion into a linear motion and then transmitting it to the support plate 506.

When the eccentric cam 511 rotates according to the operation of the motor 510, the rotational motion of the crank 512 is converted into linear motion by the power transfer transmission means 513, and then one end of the plurality of reciprocating rods 505 It is delivered to a fixed support plate 506. Therefore, the cutting member 503 reciprocates along the outer circumferential surface of the cylinder 502.

On the other hand, the polypropylene melt discharged from the homogenizer 400 is pressed into a plurality of cavities 501A configured in the guide bar 501 and then fired through each through hole 502A of the cylinder 502. At this time, when each through hole 502A of the cylinder 502 and the through hole 503A of the cutting member 503 correspond to each other according to the reciprocating motion of the cutting member 503 according to the operation of the driving unit 510, polypropylene The melt passes through each of the through holes 502A and 503A and is ignited out of the cutting member 503 for a predetermined length. Then, each of the through holes 502A and the cutting member of the cylinder 502 is transported according to the transfer of the cutting member 503. At the moment when the corresponding state of each through hole 503A of 503 is released, the foam is cut by the edge of each through hole 503A of the cutting member 503. Here, the size of the cut foam is of course determined according to the moving speed of the cutting member (503).

As such, the polypropylene is ignited and extruded through the through hole 502A of the cylinder 502, and then cut by the cutting member 503, thereby forming a pellet-shaped foam. The diameter of each through hole 502A of the cylinder 502 is 0.7 mm, and the foaming ratio is about five times the diameter of the through hole. In addition, the cutting member 503 reciprocates about 600 times per minute.

The polypropylene melt conveyed from the crushed portion 400B is under a pressure of 120 kgf / cm ² in the die portion. If the polypropylene melt in the die is immediately exposed to atmospheric pressure, the cells of the foam formed are mostly open cells. In order to prevent this, in the present invention, a decompression means is provided outside the die.

7 shows an example of the decompression means provided in the die portion. The decompression means 600 is a casing 601 which seals the discharge part 500A and the cut part 500B of the die part 500 from the outside (atmosphere). The shape of the casing 601 is not limited, and an inlet 602 through which external air is introduced is formed at one side, and an outlet 603 through which air is discharged to the outside is formed at one side thereof.

The temperature of the outside air supplied into the casing 601 is below room temperature, which can be easily maintained through a cooling device (not shown). In addition, it is of course possible to adjust the amount of air introduced by using a pump (not shown) so that the pressure in the casing 601 can maintain an appropriate degree (for example, 0.8 Kgf / cm ² ). On the other hand, the outlet 603 may be connected with the storage means for storing the pellet-shaped foam produced with the air discharged.

On the other hand, the inside of the cylinder 502 constituting the die portion 500 is very hot, and therefore the cylinder 502 must be maintained at an appropriate temperature. To this end, in the present invention, the cooling device 700 using the heat medium oil is mounted in the die portion.

FIG. 10A is a side view showing a cylinder of a die portion on which a cooling device is mounted, FIG. 10B is a front view of FIG. 10A, and the casing 601 of the decompression means shown in FIG. 7 is not shown for convenience.

The cooling device 700 used in the present invention is located in front of the cylinder 502, a ring type supply pipe 701 to which heat medium oil is supplied from the outside, and an inlet end 702A is provided with a supply pipe 701. ) And a plurality of flow pipes 702 embedded in the cylinder 502 and a discharge pipe 703 located in front of the cylinder 502 and connected to an outlet end 702B of the flow pipe 702. .

The ring-shaped heat medium oil supply pipe 701 located at the tip of the cylinder 502 is connected to a forced flow means (not shown) such as a pump so that heat medium oil of constant pressure is supplied. Thermal medium oil is injected into the flow pipe 702 through the inlet end 702A of the plurality of flow pipes 702 connected to the feed pipe 701.

A plurality of flow pipes 702 embedded at regular intervals over the entire circumference of the cylinder 502 are embedded over the entire length of the cylinder 502, the inlet end 702A and the outlet end 702B of the cylinder (502) 502) exposed to the tip. Accordingly, the heat medium oil introduced from the heat medium oil supply pipe 701 through the inlet end 702A flows along the respective flow pipes 702 over the entire length of the cylinder 502 (that is, the heat exchange is performed. After) discharged through discharge stage 702B.

The ring-shaped thermal medium oil discharge pipe 703 located at the tip of the cylinder 502 is connected at one end to a thermal medium oil storage tank (not shown), and thus flows inside the plurality of flow pipes 702. The heat medium oil, which has undergone heat exchange with the cylinder 502, flows into the heat medium oil discharge pipe 703 through the discharge end 702B and then moves to the storage tank.

Thus, the heat medium oil and the cylinder in the process of moving the heat medium oil along the heat medium oil supply pipe 701, the plurality of flow pipes 702 and the heat medium oil discharge pipe 703 embedded in the cylinder 502 The heat exchange takes place so that the cylinder can always be at a temperature suitable for foam production.

On the other hand, the reason why the supply pipe 701 for supplying the heat medium oil to each flow pipe 702 and the discharge pipe 703 into which the heat medium oil flows from each flow pipe 702 is formed in a ring shape is a cylinder having a circular cross section ( In order to simultaneously supply heat medium oil to a plurality of flow pipes 702 uniformly embedded in the circumference of the 502 and to receive heat medium oil from the flow pipe 702 at the same time, the form is a ring. Of course, it can be configured as a polygon rather than a type.

The invention will be more specifically illustrated by the following examples. However, these examples are merely embodiments of the present invention and do not limit the scope of the present invention.

Example 1

A tandem extruder consisting of a primary extruder having an internal diameter of 65 mm and a secondary extruder having an inner diameter of 90 mm was used to produce non-crosslinked pelletized polypropylene foam according to the present invention. The gear pump was connected to the end of the second extruder and subsequently a die was mounted. The die was provided with the homogenizing means shown in FIG. 3 at the point where the melt was transferred from the gear pump and the pressurizing device was provided outside the die. The hole diameter of the dice was 0.7 mm, and the pressure at the dice was maintained at 0.5 kgf / cm ² . The primary extruder was fixed at 24 rpm and the secondary extruder at 9 rpm.

40 kg of random copolymer RP2400 (propylene-3% by weight ethylene; melting index 0.25; melting point 138 ° C) purchased from YUHWA Korea Petrochemical Ind. Co., Ltd. and sodium bicarbonate purchased from Geumyang Co., Ltd. 800 g were introduced into the extruder through each hopper. 300 g of paraffin wax M1 purchased from Leo Chemical Co., Ltd. (Gimhae, Korea) was charged into a third temperature zone of the first extruder. 12 kg LPG was charged to the fourth temperature zone of the extruder using a metering pump. The temperature conditions set from the extruder to the homogenizer are as described in Table 1 below and the LD in each temperature zone is 360 mm.

 Temperature conditions Device Temperature zone Temperature (℃)  Primary extruder First 150 2nd 170 The third 170 4th 220 5th 200 6th 190  guide* 250  Secondary extruder First 170 2nd 150 The third 144 4th 139 5th 138 6th 136  Gear pump 133  Homogenizer 130

* Installed between the primary extruder and the secondary extruder, serves as a guide for transferring the melt passing through the sixth temperature zone of the primary extruder to the first temperature zone of the secondary extruder.

Example 2

The temperature conditions of the apparatus were set as described in Table 2 below and pelletized foams were produced using the same procedures and raw materials as in Example 1.

Temperature conditions Device Temperature zone Temperature (℃)  Primary extruder First 150 2nd 170 The third 170 4th 220 5th 200 6th 190  guide 250  Secondary extruder First 170 2nd 150 The third 145 4th 140 5th 138 6th 135  Gear pump 130  Homogenizer 125

Example 3

The temperature conditions of the apparatus were set as described in Table 3 below and pelletized foams were produced using the same procedures and raw materials as in Example 1.

Temperature conditions Device Temperature zone Temperature (℃)  Primary extruder First 147 2nd 167 The third 168 4th 218 5th 202 6th 1880  guide 248  Secondary extruder First 167 2nd 147 The third 142 4th 137 5th 137 6th 132  Gear pump 130  Homogenizer 129

Example 4

The temperature conditions of the apparatus were set as described in Table 4 below and pelletized foams were produced using the same procedures and raw materials as in Example 1.

Temperature conditions Device Temperature zone Temperature (℃)  Primary extruder First 151 2nd 170 The third 170 4th 219 5th 202 6th 190  guide 252  Secondary extruder First 170 2nd 150 The third 146 4th 141 5th 140 6th 135  Gear pump 130  Homogenizer 127

Example 5

The temperature conditions of the apparatus were set as described in Table 5 below and pelletized foams were produced using the same procedures and raw materials as in Example 1.

Temperature conditions Device Temperature zone Temperature (℃)  Primary extruder First 153 2nd 172 The third 172 4th 225 5th 203 6th 193  guide 255  Secondary extruder First 173 2nd 152 The third 147 4th 141 5th 142 6th 137  Gear pump 134  Homogenizer 130

Example 6

The temperature conditions of the apparatus were set as described in Table 6 below and pelletized foams were produced using the same procedures and raw materials as in Example 1.

Temperature conditions Device Temperature zone Temperature (℃)  Primary extruder First 149 2nd 170 The third 171 4th 224 5th 200 6th 191  guide 250  Secondary extruder First 170 2nd 150 The third 145 4th 140 5th 140 6th 135  Gear pump 134  Homogenizer 130

Example 7

The temperature conditions of the apparatus were set as described in Table 7 below and pelletized foams were produced using the same procedures and raw materials as in Example 1.

Temperature conditions Device Temperature zone Temperature (℃)  Primary extruder First 150 2nd 170 The third 170 4th 220 5th 200 6th 190  guide 250  Secondary extruder First 167 2nd 152 The third 142 4th 141 5th 137 6th 132  Gear pump 134  Homogenizer 130

Comparative Example 1

Using the same procedure and raw materials as in Example 1, except for the homogenizing device, the temperature conditions of the device were set as described in Table 1 below to produce pelleted foams. The temperature was set to 130 ° C. and the homogenizer was not operated. Thus, the melt from the gear pump flowed into the die through a 130 ° C. temperature zone without homogenizing.

Comparative Example 2

Using the same procedure and raw materials as in Example 1, except for the first temperature zone of the primary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foams. The first temperature zone was set at 146 ° C.

Comparative Example 3

Using the same procedure and raw materials as in Example 1, except the second temperature zone of the primary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foams. The second temperature zone was set at 173 ° C.

Comparative Example 4

Using the same procedure and raw materials as in Example 1, except for the third temperature zone of the primary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foams. The third temperature zone was set at 173 ° C.

Comparative Example 5

Using the same procedure and raw material as in Example 1, except for the fourth temperature zone of the primary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foams. The fourth temperature zone was set at 226 ° C.

Comparative Example 6

Using the same procedure and raw materials as in Example 1, except for the fifth temperature zone of the primary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foam. The fifth temperature zone was set to 205 ° C.

Comparative Example 7

Using the same procedure and raw materials as in Example 1, except for the sixth temperature zone of the primary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelletized foam. The sixth temperature zone was set at 187 ° C.

Comparative Example 8

Using the same procedure and raw materials as in Example 1, except the temperature zone of the guide, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foams. The temperature zone of the guide was set to 256 ° C.

Comparative Example 9

Using the same procedure and raw materials as in Example 1, except for the first temperature zone of the secondary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foam. The first temperature zone was set at 174 ° C.

Comparative Example 10

Using the same procedure and raw materials as in Example 1, except for the second temperature zone of the secondary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foam. The second temperature zone was set to 153 ° C.

Comparative Example 11

Using the same procedure and raw materials as in Example 1, except for the third temperature zone of the secondary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foam. The third temperature zone was set at 148 ° C.

Comparative Example 12

Using the same procedure and raw materials as in Example 1, except the fourth temperature zone of the secondary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foam. The fourth temperature zone was set to 142 ° C.

Comparative Example 13

Using the same procedure and raw materials as in Example 1, except for the fifth temperature zone of the secondary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foams. The fifth temperature zone was set to 143 ° C.

Comparative Example 14

Using the same procedure and raw materials as in Example 1, except for the sixth temperature zone of the secondary extruder, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelletized foam. The 6th temperature zone was set to 138 degreeC.

Comparative Example 15

Using the same procedure and raw materials as in Example 1, except for the temperature zone of the hunger pump, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foams. The temperature zone of the hunger pump was set to 141 ° C.

Comparative Example 16

Using the same procedure and raw materials as in Example 1, except for the temperature zone of the homogenizer, the temperature conditions of the apparatus were set as described in Table 1 below to produce pelleted foams. The temperature zone of the homogenizer was set to 131 ° C.

Experimental Example 1

The pelleted foams obtained from Examples 1 and 2 were subjected to differential scanning calorimetry (DSC) (10 ° C./min to 200 ° C., 50 cc / min to N ₂ purge) transition temperature according to the test method of KS M3050-2001. Measured. The results are shown in FIGS. 11 and 12, respectively. As can be seen from the DSC curves of FIGS. 11 and 12, the foams of Examples 1 and 2 each had a melting point of 138 ° C. of a random copolymer (RP2400 (polypropylene-polyethylene (3%)) random copolymer) used as a raw material. Lower melting points of 137.62 ° C and 128.38 ° C. DSC transition temperature was also measured for the RP2400 random copolymer as a control. The result is shown in FIG.

Experimental Example 2

Elemental analysis was performed on the pelleted foams obtained from Example 1 and the RP2400 (polypropylene-polyethylene (3%)) random copolymer as a control. This analysis was performed using a CE EA-1110 elemental analyzer. The results are shown in Table 8 below.

Elemental Analysis Results  Sample Name Analysis Items  C (%)  H (%)  N (%)  RP2400 random copolymer 85.1 15.0 ND ^*  Pellet Foam of Example 1 84.2 14.8 0.5

N.D. means non-detectable.

The detection limit of N is 0.1%.

Experimental Example 3

FT-IR analysis was performed on the pelleted foam obtained from Example 1 and the RP2400 (polypropylene-polyethylene (3%)) random copolymer as a control. This analysis was performed using a Bio-Rad Digilab FTS-165 FT-IR Spectrophotometer. The results are shown in FIGS. 14 and 15, respectively. The results of this analysis indicate that the main component of the pelleted foam and RP2400 random copolymer obtained from Example 1 is polypropylene.

Experimental Example 4

The open cell content of the pelletized foams prepared in the Examples and Comparative Examples was measured according to Procedure C described in ASTM D 2856-70. The results are listed in Table 9 below.

Experimental Example 5

The physical properties of the foams prepared in Example 1 were measured according to a conventional method, and the results are shown in Table 10 below.

Item Foam of Example 1 Magnification 25 Exterior color Pale ivory Cell size 300㎛ Extrusion strength 0.81㎏ / ㎠

Experimental Example 6

The pelleted foams obtained in Example 1 were molded using an air machine molding machine 500GF 4 with a molding pressure of 2.5 kgf / cm ² (temperature of about 138 ° C.) to produce a good molded foam. The production of such shaped foams demonstrates that the pelleted foams melt at 138 ° C. to achieve good adhesion between the foams.

Experimental Example 7

The pelleted foams obtained in Example 2 were molded using an air machine molding machine 500GF 4 with the molding pressure set at 2.4 kgf / cm ² (temperature of about 132 ° C.) to produce good molded foams. The production of such shaped foams demonstrates that the pelleted foams melt at 132 ° C. to achieve good adhesion between the foams.

From the above description, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. In this regard, it should be understood that the embodiments and experimental examples described above are illustrative in all respects and not restrictive. The scope of the present invention should be construed that all changes or modifications derived from the meaning and scope of the appended claims and their equivalents, rather than the detailed description, are included in the scope of the present invention.

The non-crosslinked pelletized polypropylene foams according to the invention comprise at least 80% closed cells and are very useful in terms of molding and regeneration as they have a melting point of 125 ° C to 140 ° C.

1 is an overall configuration diagram of a foam manufacturing apparatus according to the present invention.

FIG. 2 is a plan view illustrating a cylinder of the first extrusion part 100 illustrated in FIG. 1.

3 is a cross-sectional view taken along the line A-A of FIG. 2.

4 is a schematic configuration diagram of a CO ₂ supply apparatus.

5 is a cross-sectional view illustrating an internal structure of the pumping unit 300 and the homogenizer 400 shown in FIG. 1.

6A and 6B are front views illustrating each member of the homogenizer 450.

FIG. 7 is a plan view illustrating a structure of the dice part 500 illustrated in FIG. 1.

8 is a cross-sectional view taken along the line B-B of FIG. 7.

9 is a cross-sectional view taken along the line C-C of FIG. 8.

It is a side view which shows the cylinder of the dice | dies part with a cooling apparatus.

10B is a front view of FIG. 10A.

11 is a DSC curve of pelletized polypropylene foam (Example 1) prepared according to the present invention.

12 is a DSC curve of pelletized polypropylene foam (Example 2) prepared according to the present invention.

Figure 13 is a DSC curve of the RP2400 (polypropylene-polyethylene (3%)) copolymer used to prepare the pelletized polypropylene foam of the present invention.

14 shows the results of FT-IR analysis of pelletized polypropylene foams prepared according to the present invention.

15 shows the results of FT-IR analysis of the RP2400 (polypropylene-polyethylene (3%)) copolymer used to prepare the pelletized polypropylene foam of the present invention.

16A is a 100-fold optical micrograph of a pelletized polypropylene foam made in accordance with the present invention.

16B is a 400x optical micrograph of pelletized polypropylene foam made in accordance with the present invention.

<Description of the symbols for the main parts of the drawings>

100: extruder 101: cylinder

101a: inlet 101b: inlet

101c: outlet 101d: inlet

102 drive unit 103 screw

104: cooling means 105: heating means

110A: CO ₂ storage tank 110B: refrigeration unit

110C: CO ₂ supply unit 110D: CO ₂ stabilization unit

110E: storage unit 200: extruder

201: cylinder 300: pumping part

301: Casing 302A, 302B: Gear

303 drive unit 400 homogenizing unit

400A: rotating part 400B: crushing part

401: first housing 402: driven sprocket

403: drive sprocket 404: drive part

405: bearing block 406: bearing block

407: support plate 408: support plate

409: support plate 410: screw

411: second housing 412: frame

412A: Inlet port 412B: Outlet port

450: homogenization means 451: rotating plate

451A: incision 452: fixed plate

452A: circular opening 500: dies

500A: discharge part 500B: cutting part

500C: drive unit 501: guide bar

501A: Cavity 502: Cylinder

502A: Through Hole 502B: Groove

503: member 503A: through hole

505: reciprocating rod 506: support plate

510: motor 511: eccentric cam

512: crank 513: power change transmission means

600: decompression means 601: casing

602: inlet 603: outlet

700: cooling device 701: supply pipe

702: flow pipe 702A: inlet end

702B: discharge stage 703: discharge pipe

Claims (4)

Melting point is 125 to Uncrosslinked pelleted polypropylene foam at 140 ° C. The non-crosslinked pelletized polypropylene foam of claim 1 having at least 80% closed cells. The non-crosslinked pelletized polypropylene foam according to claim 1 or 2, wherein the melting point is 125 ° C to 130 ° C. The non-crosslinked pellet polypropylene foam according to claim 1, wherein the proportion of comonomers other than propylene in the propylene random copolymer is 0.05 to 10% by weight.