KR20070011948A - Polyolefin foams having improved property - Google Patents

Abstract

Provided are polyolefin foams, which exhibit excellent properties such as flexibility, heat resistance, creep resistance, and damping performance and are useful for shock and noise-blocking materials. The polyolefin foam comprises 40-95wt% of expandable polyolefin resin and 5-60wt% of a characteristic change resin. The characteristic change resin is at least one resin selected from the group consisting of polybutene-1 resin and styrene-olefin block copolymer. The polyolefin foam has a density of 9-100kg/cm^3. The expandable polyolefin resin is low density branched polyethylene resin. The polybutene-1 resin is at least one resin selected from the group consisting of polybutene-1 homopolymer and copolymer of butene-1 and other olefin. The styrene-olefin block copolymer is styrene-isobutylene block copolymer.

Description

Polyolefin foams having improved property

1 is a diagram showing the thermal deformation characteristics of the mixed polymer foam of the present invention.

2 is a view showing the storage modulus of the mixed polymer foam of the present invention.

3 is a view showing the clamping performance of the mixed polymer foam of the present invention.

The present invention relates to a polyolefin foam having improved physical properties, and more particularly, to a polyolefin foam prepared by foaming a mixture of a property-variable resin in an expandable polyolefin resin in order to improve flexibility, heat resistance, creep resistance and damping performance. will be.

In general, foams are used in many applications, including the manufacture of shaped articles such as insulation, sound insulation, shock absorbers, cups or dishes. It is preferable that a foam has at least one or more characteristics required for the use. For example, when the foam is used for impact noise isolation, the flexibility and damping performance of the foam is important.

In addition, foams used in high temperature environments such as insulation should have adequate heat resistance (high heat deformation temperature), and foams used for shock absorbing or noise blocking at high temperatures should also have heat resistance and flexibility. Such flexibility and heat deflection temperatures vary depending on the end use of the foam. For example, when used in automobiles or used for thermal insulation of hot water pipes, a heat deflection temperature of 90 ° C. or higher is required, and in some cases a flexible foam having a high heat deflection temperature of 110-120 ° C. or higher is required.

However, it is difficult to simultaneously obtain high flexibility properties (ie low modulus of elasticity) and high heat distortion temperatures in foams made of one resin. In general, both the flexibility (ie modulus of elasticity) and the heat distortion temperature of one resin are directly related to the melting point of the resin. That is, resins having a low modulus of elasticity (ie, high flexibility) generally have a low melting point, and resins having a high modulus of elasticity exhibit high melting points. Although one resin or resin mixture may have high flexibility and heat resistance at the same time, in this case, it is difficult to foam the resin or resin mixture by a convenient process such as a general extrusion process.

On the other hand, the side chain polyoletin resin produced by the free radical (free radical) process can be foamed into a flexible foam by extrusion, but this foam has a problem that the temperature resistance is insufficient in certain cases. One example of the branched polyolefin resin is a low density polyethylene homopolymer resin in the range of 0.915 to 0.932 g / cm ³ .

Such as high density polyethylene, isotactic polypropylene, polybutene-1 resins produced by catalytic processes (eg using Ziegler Natta or metallocene catalysts) Although the linear polyolefin homopolymer resin has a relatively high heat deformation temperature, it is difficult to foam by a general extrusion process. In addition, the foam produced by such a high density homopolymer resin has a problem of low flexibility.

On the other hand, it is possible to produce a linear polyolefin copolymer resin excellent in low-density flexibility by the catalytic process, there is a problem that such a linear polyolefin copolymer resin also lacks the foaming capacity like the homopolymer.

In addition, the service temperature of the polyolefin resin foam can be increased by crosslinking. For example, crosslinkable foams made from low density polyethylene resins are used at higher temperatures than noncrosslinkable foams. However, the use temperature of these foams is 100 ° C. or less, which is not high enough in certain cases, crosslinkable foams are expensive to produce them, and there is a problem that recycling is impossible.

In addition to high thermal deformation temperatures, load resistance is an essential characteristic in foams used in supporting loads, with the use of shock absorbing and impact sound reduction. Flexible foams are increasingly used as sound insulation in "floating floor structures" designed to prevent the transmission of impact sounds. To be effective sound insulation in this structure, the foam must have high flexibility (low modulus of elasticity), and the "screed load" applied on the foam and the "traffic load" due to human traffic. It must be able to withstand, and sufficient creep resistance to these loads is also essential. According to the European Standards EU 1991, "passage loads" are measured in the range of 2 to 5 kPa depending on the type of building and the application used. Therefore, creep resistance is generally measured at 3.5 kPa, which is an average value.

In order to define the suitability of the product to be used under these various traffic conditions, the European Union has elaborated on the compression test method in the European standard EN 12 431. According to this criterion, compressibility means that the specimen thickness (dL) under almost no load (significant load of 0.25 kPa) and high load (2 minutes under 2 kPa load and 2 minutes under 50 kPa load) Afterwards, it is represented by the difference (dL-dB) of the thickness (dB) measured under a load of 2 kPa, and a product having low compressibility, that is, a product having a good recovery of thickness after receiving a load is preferable. For example, where the transit load is 2 kPa or less, a product with a thickness dL of 35 mm or less should not have a compressibility higher than 2 mm. A 20 mm thick product with a brief 50 kPa load on the living room floor should be less than 2 mm under a 2 kPa load.

In addition, the EN 12 431 test method relates to the stimulation of relatively transient loads. In conditions such as the living room of a residential building, the load on it remains longer. For example, heavy cabinets or furniture have been in place for long periods of time, and in such long load situations, consideration should be given to the creep phenomenon of the sound insulation. There is no international standard defined for creep resistance requirements for floor sound insulation. However, it is evident that the sound insulation should not be overly deformed during long term use. Basically, the creep of the sound insulation is dependent on the load applied and its duration. In general, the weight on the residential floor is represented by a load of 3.5 kPa, which actually lasts for many years. In laboratory screening experiments, the experimental period is generally set to 1,000 hours (41.7 days). Floor sound insulation with creep resistance suitable for practical use should have a creep less than 20%, preferably less than 10% and more preferably less than 5% in this laboratory experiment.

At present, polypropylene foams and low density polyethylene foams that have been softened and compressed into floor insulation are commonly used. Even if compression softened, EPS moldings are still rigid, and low density polyethylene foams have a problem of lack of creep resistance. Thus, there is a need for sound insulation materials that can satisfy both low modulus and sufficient creep resistance. In addition, the foam material preferably has excellent damping properties in order to prevent the transmission of impact noise at low frequencies. Heavy impacts on the floor generate low frequency noise, which is often amplified by the ringing of the floating floor structure, and therefore requires a foam material with damping properties that can dampen the ringing. Therefore, the preferred impact noise shielding material preferably has low modulus of elasticity, low creep and high damping characteristics. Low-density polyethylene foam meets most of the conditions of low modulus of elasticity, but has a problem of low creep and high damping ability.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems as described above, and to provide a foam material having excellent flexibility, heat resistance, creep resistance and damping performance while being foamed by a convenient process such as an extrusion process.

In order to achieve the above object of the present invention, the polyolefin foam having improved physical properties of the present invention comprises 40 to 95% by weight of the expandable polyolefin resin, and 5 to 60% by weight of the property variation resin, wherein the property variation resin Is at least one resin selected from the group consisting of polybutene-1 resin and styrene-olefin block copolymers, wherein the polyolefin foam is characterized in that the density is 9 ~ 100kg / m ³ .

Here, the polyolefin foam is characterized in that the density is 15 ~ 50kg / m ³ , wherein the expandable polyolefin resin is characterized in that the low density side chain polyethylene resin, the polybutene-1 resin is polybutene-1 homopolymer and At least one resin selected from the group consisting of butene-1 and copolymers of other olefins, wherein the styrene-olefin block copolymers are styrene-isobutylene block copolymers.

In addition, a nucleating agent, a foaming agent and a dimensional stabilizer are further added to the mixture of the above-mentioned expandable polyolefin resin and the above-mentioned characteristic variant resin.

The present invention provides a mixed polymer foam prepared by mixing a property variant resin with an expandable polyolefin resin and then extruding the mixture. The mixed polymer foams of the present invention exhibit desirable combinations of properties that have been difficult to obtain until now. The expandable polyolefin resin enables the foaming of the mixed polymer, and the property variant resin imparts properties such as flexibility, high deformation temperature, improved creep resistance and damping performance without compromising the foaming performance of the expandable polyolefin resin. These properties are the properties required for many applications, including the prevention of collision noise.

Here, the expandable polyolefin resin used in the present invention includes all kinds of polyolefin polymers that can be easily foamed by an extrusion process. Branched chain polyolefin resins such as ethylene homopolymers and copolymers prepared by a free-radical high-pressure process are free foamable polyolefin resins suitable for use in the present invention and have high melt strength (HMS: high). Modified polypropylene resins whose viscosity is modified to have melt strength are also suitable for use as the expandable polyolefin resin of the present invention. Particularly preferred are expandable polyolefin resins having a melt index of 0.1 dg / minute to 20 dg / minute, which shows the flowability of the molten resin, of which resins having a melt index of 0.2 dg / minute to 10 dg / minute are particularly preferred. desirable. If the melt index is lower than 0.1 dg / minute, the viscosity of the resin is too high. When extruding the foam, high pressure is required to extrude the foam, making it difficult to extrude the foam. In the case of crosslinked foaming, mixing the foaming agent or manufacturing a sheet Phosphorus melt processing is difficult. If the melt index is higher than 10 dg / minute, the viscosity of the resin is so low that it is difficult to maintain the required pressure in the die in the case of extrusion foaming, and in the case of crosslinked foaming, it is difficult to obtain the appropriate crosslinking density necessary for the stability of the foam with the crosslinking agent. .

Among the ethylene copolymers, ethylene / vinyl acetate copolymers are preferred, especially ethylene / vinyl acetate copolymers containing 5-30% of vinyl acetate. One example of a polypropylene resin with a suitable HMS is a PRO-FAX PF-814 grade resin supplied by Basell Polyolefins. One example of a suitable ethylene / vinyl acetate copolymer resin is Elvax 460 ™ resin from DuPont-Dow Elastomers Inc.

In addition, one of the property-variable resins used in the production of the polyolefin foam having the physical properties according to the present invention is a polybutene-1 resin. An example of such a polybutene-1 resin is polybutene (PB) resin supplied by Basel Polyolefins. The commercialized polybutene (PB) resin is a homopolymer of butene-1 or a copolymer of butene-1 and a small amount of ethylene.

Through experiments of the present invention, it was found that the polybutene-1 resin is easily foamed when mixed with low density polyethylene, and the mixed foam has temperature resistance, creep resistance and improved damping properties. In addition, polybutene-1 resin hardly interferes with the foaming of polyethylene due to the slow crystallization rate of the resin. It is not clear whether the polybutene-1 resin crystallizes at ambient temperature during the maturation of the foam, but given that the mixture foams have a low modulus of elasticity, this indicates that the polybutene-1 resin component is completely crystallized during the maturation of the foam. It is not supposed to be. Surprisingly such mixed resin foams have a high heat deflection temperature derived from polybutene-1 resins even though the polybutene-1 resin will be in an amorphous state. Accordingly, polymer foams produced from mixtures of expandable polymer resins and polybutene-1 resins are the most preferred embodiments of the present invention.

In addition, another of the property-modified resins used in the production of polyolefin foams having improved physical properties according to the present invention are styrene-olefin block copolymers, which are rubber resins. An example of such a rubbery resin is Kraton (trade name) resin manufactured by Shell Chemical Company. For example, Kraton 1652 is a styrene-ethyline / butylene-styrene tri-block copolymer. Recently, Kaneka Corporation of Japan has begun to market styrene-isobutylene (SIBS) block copolymer called Sibstar (tradename).

Experiments of the present invention have confirmed that the mixture of SIBS resin and polyethylene resin provides excellent foam with high heat distortion temperature. Accordingly, foams made from mixtures of expandable polyolefin resins and SIBS resins are preferred embodiments of the present invention.

In addition, in order to enhance the creep resistance of the mixture foam, a small amount of polybutene-1 resin can be further mixed and used in the mixture of the expandable polyolefin resin and the SIBS resin. Therefore, foams made from triple mixtures of expandable polyolefin resins, SIBS resins and polybutene-1 resins are another embodiment of the present invention.

The damping performance of the foams can be obtained not only from polymers with inherent damping performance but also from polymer mixtures. All polymers have maximum damping performance near the glass transition temperature (Tg). Mixing two or more inexpensive polymers with significantly different glass transition temperatures is expected to expand the range of glass transition temperatures and dampen noise and vibration over a wider range of frequencies and temperatures.

In addition, the foam of the present invention may optionally add a nucleating agent to the foam resin mixture in order to control bubbles. The amount of nucleating agent added to prepare the foam of the present invention depends on the preferred bubble diameter, foaming temperature and the constituents of the nucleating agent, and available nucleating agents include calcium carbonate, barium stearate, calcium stearate, talc, earth, titanium dioxide , Silica, diatomaceous earth, citric acid mixture, bicarbonate and sodium bicarbonate. In use, the amount of nucleating agent consumed is 0.01 to 5% by weight of the polymer resin mixture, which controls the bubble diameter of the foam to a size of 0.01 to 15 mm.

In addition, a foaming agent is added during preparation to foam the foam of the present invention. In this case, the blowing agents used include inorganic blowing agents which are all kinds of blowing agents known in the art, physical and chemical blowing agents including organic blowing agents, and mixtures thereof. Suitable inorganic blowing agents include carbon dioxide, nitrogen, argon, water, air and helium, and organic blowing agents include aliphatic hydrocarbons having 1 to 6 carbon atoms, aliphatic alcohols having 1 to 3 carbon atoms and fully or partially halogenated 1 to 4 carbon atoms. Aliphatic hydrocarbons having 2 carbon atoms. The aliphatic hydrocarbons include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane and neopentane. Aliphatic alcohols include methanol, ethanol, n-propanol and isopropanol. Fully or partially halogenated aliphatic hydrocarbons include chlorocarbons, fluorocarbons, chlorofluorocarbons. Chlorocarbons used in the present invention include methyl chloride, methylene chloride, ethyl chloride and 1,1,1-trichloroethane. Fluorocarbons used in the present invention are methyl fluoride, methylene fluoride, ethyl fluoride, 1,1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HGC-143a), 1,1,1 , 2-tetrafluoroethane (HFC-134a), 1,1,2,2-tetrafluoroethane (HFC-134), pentafluoroethane, perfluoroethane, 2,2-difluoropropane, 1,1,1 -Trifluoropropane and 1,1,1,3,3-pentafluoropropane. Partially halogenated chlorofluorocarbons used in the present invention include chlorodifluoromethane (HCFC-22), 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC142b), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). Fully halogenated chlorofluorocarbons may also be used, but are not preferred for environmental reasons. Chemical blowing agents used in the present invention are azodicarbonamide, azodiisobutyronitrile, benzenesulfonhydrazide, 4,4-oxybenzene sulfonyl-semicarbazide, p- Toluene sulfonyl semi-carbazide, N, N'-dimethyl-N, N'-dinitrosoterphthalamide, trihydrazine triazine, sodium bicarbonate and a mixture of sodium bicarbonate and citric acid. Mixtures of all these blowing agents can also be used within the scope of the present invention. The form of the most suitable blowing agent depends on the process used to prepare the foam and the desired density of the foam. Preferred blowing agents in the extrusion process and in the batch process for producing EPS are physical blowing agents, with double volatile organic blowing agents being preferred. Among the volatile organic blowing agents, propane and isobutane and mixtures of these blowing agents with n-butane, n-pentane or isopentane are most preferred. For the crosslinked foam process, decomposable blowing agents which release nitrogen or decomposed nitrogen are most preferred.

The amount of blowing agent added to the polymer melt to prepare the foam-forming gel is 0.1 to 5 gmole / kg (gmoles per kg of polymer), preferably 0.4 to 4 gmole / kg, most preferably 0.9-3 gmole / kg, which controls the foam density to 9-100 kg / m ³ .

In addition, the foam according to the present invention preferably exhibits dimensional stability, and it is preferable to add a stability control agent to enhance the dimensional stability. Dimensional stabilizers are particularly preferred for the production of foam blocks in the form of thick sheets or plates of closed-cell structure from the aforementioned mixtures. Dimensional stabilizers, on the other hand, are not needed when foaming open-celled foams. Preferred dimensional stabilizers include amides and esters of (C ₁₀ -C ₂₄ ) fatty acids having 10 to 24 carbon atoms, such dimensional stabilizers are shown in US Pat. Nos. 3,644,230 and 4,214,054. Most preferred dimensional stabilizers include stearyl stearamide, monostearate glycerol (glocerol monostearate), glycerol monobehenate and sorbitol monostearate. In general, such a dimensional stabilizer is added in an amount in the range of 0.1 to 10% by weight of the polymer, wherein when the amount of the dimensional tablet is added to 0.1% by weight or less, it is difficult to prevent the shrinkage of the foam, the amount of the dimensional stabilizer When added in an amount of 10% by weight or more, the amount is too large to make extrusion difficult, and the physical properties of the product are lowered, such as being soaked into the surface of the foam and transferred to the object.

In addition, various various additives may be added to the foam, such as inorganic fillers, pigments, antioxidants, acid trapping agents, ultraviolet absorbers, flame retardants, process aids, extrusion aids.

The mixed polymer foams of the present invention may be prepared by techniques and procedures known to those skilled in the art, which procedures may include extrusion processes, batch processes, crosslinkers, and decomposition for producing expandable beads using physical organic blowing agents. A process using possible blowing agents. Of these processes, the extrusion process is most preferred.

The mixed polymer foams of the present invention may be crosslinked foams or noncrosslinked foams. The manufacturing process of polymer foams was described in 2004 by Hanseo Publishing Co. in Munich. Klempenner and V. Chapter 8, "Polyolefin Foam," Chapter 8, Handbook of Polymer Foams and Foam Technology, 2nd edition of the Handbook on Polymer Foams and Foam Technology, edited by Sendillarevic and written by the inventors 2nd Ed., D. Klempner and V. Sendijarevic, Hanser Publishers, Munich 2004).

The noncrosslinked foams of the invention are prepared by conventional extrusion foaming processes. In the extrusion foaming step, the premixed expandable polyolefin resin and the property change resin are melt mixed in the extruder, and then a blowing agent is added thereto under pressure to lower the temperature, and extrude through a die to foam. At this time, the resin mixture is heated to a temperature above the melting point before mixing with the blowing agent, and the blowing agent is added to the polymer melt and mixed by means known in the art such as an extruder, a mixer, a mixer. At this time, the mixing of the resin mixture and the volatile blowing agent should be carried out under pressure so that the blowing agent is not vaporized in the extruder, and the pressure of the extruder must be maintained so as not to expand until the mixture mixed with each other is discharged out of the die. In addition, when a nucleating agent is added, it is added to the powder in the form of a solid resin before the resin mixture is calcined or melted. Generally, the expandable gel (homogeneous mixture of melted resin and blowing agent) is cooled to an appropriate temperature to obtain a stable bubble, and then extruded into a low pressure space through a die having a suitable shape and size. In this case, the low pressure may be higher than the atmospheric pressure or in a vacuum state, but the most common case is the atmospheric pressure.

When the non-crosslinked foam of the present invention is produced by an extrusion process, it is possible to prepare strand aggregates in which foam strands are stuck together using a multi-orifice die. In order to produce foam strand assemblies, the holes in the die must be arranged closely so that the foam strands to be expanded can adhere to form a single foam structure. Apparatus and methods for making such foam strand assemblies are shown in US Pat. Nos. 3,573,152 and 4,324,720.

In addition, the foam of the present invention may be made of non-crosslinked foam beads suitable for molding molding. There are a number of methods for producing such foam beads, which are described in Chapter 8, "Polyolefin Foam," in the second edition of the Handbook of Polymer Inventors and Foam Technology of the Invention described above. For example, non-crosslinked foam beads are produced by an extrusion process or a batch process. In the extrusion process, a multi-hole die is attached to the extrusion foaming device so that the foam strands do not stick to each other, and the foam strands exiting the hole are cut with a knife passing through the die surface. To prepare. In addition, in a batch process, the volatile blowing agent is deposited on granulated resin particles floating in a water solvent in an autoclave or other pressure vessel, and then rapidly released into the low pressure space through an appropriately sized outlet at a suitable temperature. Manufacture. Such a process is described in detail in US Pat. Nos. 4,379,859 and 4,464,484.

The crosslinkable foams of the present invention can be produced by crosslinkable foam processes using degradable blowing agents or by conventional extrusion processes. The crosslinked foam process using a degradable blowing agent includes a chemical crosslinking process and a radiation crosslinking process. In the case of the chemical crosslinking process, the resin mixture, the crosslinking agent and the chemical blowing agent are mixed at a low temperature, and then extruded into a sheet form through a die, and the sheet is heated in two steps to crosslink and foam. In the case of radiation crosslinking, the extruded sheet is irradiated with an electron beam without the crosslinking agent and necessary crosslinking is performed. Here, the chemical crosslinking is a method using a silane chemical in addition to the method using a peroxide chemical, and regarding the crosslinked foam manufacturing process, the handbook on the polymer foam and the foam technology, which the author of the present invention is the author It is described in detail in Chapter 8 of the second edition.

The crosslinked foams of the invention can also be produced continuously by extrusion processes using long-land dies described in British Patent Application GB 2,145,961A. In the extrusion process, the polymer, degradable foaming agent and crosslinking agent are mixed in a extruder, heated and melted, and the polymer resin is crosslinked and the foaming agent is decomposed while moving through a long die, and a foam is formed. It is lubricated by the lubrication material supplied from to allow the foam to exit through the die.

In addition, the crosslinked foams of the present invention may be made of crosslinked foam beads suitable for molding. There are several methods for producing the crosslinked foam beads, for example, after granulating the resin particles in the water of an autoclave or other pressure vessel, the crosslinking agent and the blowing agent are deposited therein to cause crosslinking, and the appropriate foaming temperature. After the designation, it is released quickly into the atmosphere or low pressure space to be foamed. Another variation of this process is to impregnate the polymer beads with a blowing agent, hold them at a low temperature, release them from the vessel without cooling the beads, and expand using steam or hot air. Another modification process involves impregnating the styrene monomer with the crosslinking agent in the floating polyolefin resin granules in the above-described process to form an interpolymer with the resin, and then depositing the blowing agent to produce the expandable resin beads.

A method for producing a bead molding includes a method of filling a mold with foam beads, compressing the mold, and heating the product with steam, or increasing the internal pressure by infiltrating air into the foam beads, and then heating and molding the mold into a mold. . Regarding the process and the molding method, pages 278 ~ 281 of the second handbook of the polymer foam and foam technology, which the authors mentioned above are the authors, and US Patent Nos. 3,886,100, 3,959,189, 4,168,353 and 4,429,059 It is explained in detail in. Foam beads can also be prepared by preparing a mixture of polymer, crosslinking agent and degradable chemical foaming agent in a suitable mixing apparatus or extruder, preparing the mixture into particles, heating, and then crosslinking and expanding.

The following specific examples are intended to illustrate the invention, but are not intended to limit the scope of the invention. In the examples,% is by weight unless otherwise indicated or unless content is required.

Foam extrusion equipment

The apparatus used in this embodiment is a tandam foam extrusion line consisting of a twin screw primary extruder of 30 mm diameter and a single screw cold extruder of 40 mm diameter. The primary extruder is a 40D long Leistritz LSM34 model extruder that includes a mixing section followed by a conventional feed, melt and metering section, and the inlet for blowing agent is located 19D away from the resin supply. Formed. The primary extruder includes a total of eight heating sections, and the cooling extruder also includes three cooling sections in a 40D barrel. A rectangular die orifice is attached to the end of the cold extruder, and the die orifice is 6 mm wide and 3 mm long.

Used polymer resin

The polymer resins used in the tests of this example are shown in Table 1 below.

Display designation Source Melting indicators Melt Index Condition (℃) Explanation LDPE PE 640i Dow Chmical Co. 2.3 190 Low density side chain polyethylene PBc PB-8640 Basell Polyolefins 0.9 190 Butene-1: Copolymer having an ethylene ratio of 98: 2 PBh PB-0300 Basell Polyolefins 3.7 190 Polybutene-1 Homopolymer SIBS SIBSTAR 073T Kaneka Corporation 7 230 Styrene-isobutylene block copolymer

Foam composition

The foam composition used for the foam extrusion test is shown in Table 2 below. For dimensional stabilization of the foam, in all tests, 1 part by weight of glycerol monostearate (Pationic 1052 brand available from American Ingredients), a dimensional stabilizer per 100 parts by weight of polymer resin, was used. Is added. In addition, small amounts of barium stearate and talc powder are added to control the cell size. The concentration of the barium stearate is fixed at 0.1 pph (11 parts by weight per 100 parts by weight of polymer) throughout the entire test, the concentration of the talc powder in Test 1 is 0.4 pph and 0.5 pph in the remaining tests.

Test No. Polymer component ratio (% by weight) Foaming agent (parts by weight) Foaming Temperature (℃) Foam thickness (mm) Density (kg / m ³ ) Bubble diameter (mm) One LDPE = 100 11.5 104 26 35 2.7 2 LDPE: PBc = 50: 50 11 104 21 41 1.8 3 LDPE: PBh = 50: 50 11 103 24 45 1.4 4 LDPE: SIBS = 70: 30 11 103 24 41 1.4 5 LDPE: PBh: SIBS = 50: 30: 20 11 103 24 42 1.4

In Table 2, Test 1 is a low density branched polyethylene (LDPE: Comparative Example), as shown in Table 1, PBc (Polybutene-1 copolymer) is a polybutene-1 copolymer, PBh ( Polybutene-1 homopolymer (polybutene-1 homopolymer) is a polybutene-1 homopolymer, SIBS (Styrene-isobutylene block copolymer) is a styrene-isobutylene block copolymer.

In addition, the polymer component ratio represents the ratio (% by weight) of the modified polymer mixed in the low density side chain polyethylene (LDPE), for example, Test 5 includes 30% by weight of PBh and 20% by weight of SIBS in 50% by weight of LDPE. Indicates that

The blowing agent is a mixture of isobutane: n-pentane at 70:30 and represents the amount of blowing agent added per 100 parts by weight of the polymer. The foaming temperature represents the temperature of the last cooling part of the foam extrusion apparatus, the foam thickness is the thickness measured after the foam has aged for about a month, and the bubble diameter is the value measured by ASTM D-3576.

The amount of the blowing agent exemplified in this embodiment is 1.78 ~ 1.86gmole / kg in terms of gmole per kg of the polymer, it can be seen that it is within the threshold range of the blowing agent described above.

The foams presented in this example relate to non-crosslinkable foams without addition of a crosslinking agent. Although not illustrated in this embodiment, it is also possible to produce crosslinkable foams in this manner by adding a crosslinking agent.

Foam extrusion

In practice, the primary extruder is operated with all parts kept at 200 ° C., and the rotational speed of the extruder screw is gradually increased to 40 rpm. Operation of all three parts of the cold extruder was set to 175 ° C. and the rotational speed of the cold extruder screw was adjusted to 25 rpm.

As described above, the granular polymer mixture in a predetermined ratio is premixed with dimensional stabilizer monostearate glycerol and nucleating agent barium stearate or talc powder and fed to the primary extruder at a uniform rate of 2.94 kg per hour. The blowing agent mixed with isobutane and n-pentane in a 70:30 weight ratio is injected into the mixing section of the extruder at a rate of about 11 pph. When the extrusion state is stable, the temperature of the cooling section is gradually lowered until the optimum foam is obtained. When the first two cooling sections were set at 140 ° C and the last cooling section at 103 ~ 104 ° C, an optimum foam having an independent bubble structure was obtained, and the foam showed satisfactory dimensional stability.

In addition, in Table 2, it can be seen about the processability of the mixture foam produced through such foam extrusion process. That is, the width of the foam strand is about 30 mm, the thickness is in the range of 21 to 26 mm, the bubble diameter of the foam is in the range of 1.4 to 2.7 mm, and the density of the foam is 35 to 45 kg / m ³ .

compression Foam  Measure heat resistance, flexibility and compression

The foam is aged for about a month before the physical property test begins. In order to measure the heat deflection temperature, the foam strand is cut into 3 cm lengths to make a specimen, and the specimen is heated in a reflux oven at various predetermined temperatures for 1 hour, and then the volume change of the foam specimen is measured by the buoyancy method. It was. The highest temperature at which this foam specimen does not shrink by more than 5% is the heat deflection temperature.

In addition, the sides of the foam strands were cut out and the strands were attached to each other using hot air to prepare foam pads, and the upper and lower portions of the foam pads were cut in a hot wire cutter to prepare a flat shape. Then, this pad was cut into a rectangular shape having one side of about 6-8 cm to prepare a test specimen for compression. The specimens thus prepared were approximately 16-18 mm thick, and these specimens were used to measure compressive properties such as compressive modulus, compressive strength and creep.

The compressive strength was measured at a compression rate of 20 mm per minute by a method corresponding to ASTM D 3575 D method. This compression test was conducted at room temperature of about 25 ° C., and the compressive modulus was measured at a compression rate of 500 mm per minute in order to simulate the dynamic modulus. The compressive modulus of elasticity is measured from the initial elastic strain portion of the stress strain curve.

The physical properties of the foams produced in this embodiment are shown in Table 3 and FIG. 1 below, all of which have at least one desirable property.

Test No. Polymer component ratio (% by weight) Heat Deflection Temperature (℃) Compressive modulus of elasticity (kPa) Compressive strength Compressibility (mm) Creep (%) 5% (kPa) 10% (kPa) 25% (kPa) One LDPE = 100 110 716 25 42 56 1.0 7.0 2 LDPE: PBc = 50: 50 110 357 15 26 44 1.5 1.5 3 LDPE: PBh = 50: 50 125 653 24 42 63 1.7 2.7 4 LDPE: SIBS = 70: 30 125 270 11 22 38 1.7 4.5 5 LDPE: PBh: SIBS = 50:30:20 120 257 12 18 29 1.9 6.0

In Table 3, Test 1 is a comparative example, and the heat distortion temperature is a heat deformation, which indicates the maximum temperature at which the foam shrinks by 5% or more during an exposure time of one hour. In addition, the compressive elastic modulus represents the flexibility of the foam, which is a value measured by ASTM D 3575 D when compression deformation at a compression rate of 500 mm per minute. In addition, the compressive strength is a value measured at a compression speed of 20 mm per minute, the compressibility is a value determined by the European standard EN 12 431, and the creep is deformed compared to the original thickness when a load of 3.5 kPa is applied for 1,000 hours. The ratio of thickness is shown.

As can be seen from Table 3, in this example, the heat deflection temperature is 110 ° C. for test 1, 110 ° C. for test 2, 125 ° C. for test 3, 125 ° C. for test 4, and 120 for test 5 It was found to be ° C. The mixture foams in which PBh or SIBS were mixed in LDPE of Tests 3 to 5 except the foams prepared from the mixture of the low density side chain polyethylene and the polyputene-1 copolymer (PBc) of Test 2 consisted of only the low density side chain polyethylene with a heat deflection temperature. 10-15 ° C. higher than foam. Therefore, it can be seen that the foam formed by mixing PBh or SIBS in the low density side chain polyethylene has improved heat resistance compared to the foam made of LDPE alone.

In addition, as can be seen from Tables 2 and 3, the mixture foam was 41-45 kg / m ³ , although the mixture foam was 17-30% higher than the density of 35 kg / m ³ , which is a foam composed solely of low-density side chain polyethylene. The compressive modulus of is 357 kPa for test 2, 653 kPa for test 3, 270 kPa for test 4, and 257 kPa for test 5, which is less than the compressive modulus of 716 kPa for foams consisting solely of low-density side chain polyethylene. More flexible than foams consisting only of polyethylene. Therefore, it can be seen that the foam formed by mixing PBc, PBh or SIBS in the low density side chain polyethylene has improved flexibility compared to the foam made of LDPE alone.

In particular, the remaining foams, except for the mixture foam of low density polyethylene and polybutene-1 homopolymer (PBh) of Test 3, which are almost 30% more dense than the low density side chain polyethylene foam, are 1/3 to 1/2 of the foam consisting of only low density polyethylene. Low compressive modulus in the range.

In addition, all foams in Table 2 exhibit satisfactory compressibility of up to 2 mm in the EN 12 431 compressibility test, and mixture foams have a low compressive modulus and low compressive strength compared to LDPE-only foams. The creep was relatively low. Therefore, it can be seen that the foam formed by mixing PBc, PBh, or SIBS with low density side chain polyethylene is improved in creep resistance compared to the foam made of LDPE alone.

Dynamic mechanical properties

The dynamic mechanical properties of the mixed polymer foams prepared in this example were measured using a Model 2980 thermal mechanical analyzer from TA Instruments, Inc. (New Castle, Delaware, USA). . Cylindrical foam specimens having a diameter of about 15 mm and a thickness of about 6.2 mm were prepared from the foam strands and pressed in the direction perpendicular to the compression direction to measure the dynamic mechanical properties.

Dynamic mechanical properties were measured by vibration compression of 50 Hz while raising the temperature at a rate of about 5 ° C. per minute, and the degree of deformation was fixed at about 0.8% of the thickness. Through this embodiment, the storage modulus (E '), loss modulus (E "), and tan delta (tan δ) of the polymer foam can be measured, and the dual storage modulus (E') is the copper of the object. The tan delta (ie, loss factor), which represents the modulus of elasticity and is the ratio of the loss modulus (E ") to the storage modulus (E '), indicates the damping performance of the material against impact.

The storage modulus (E ') and tan delta values are shown as a function of temperature in FIGS. 2 and 3, respectively, and Table 4 below shows the properties of the polymer foam measured at particular temperatures of 0 ° C, 20 ° C and 40 ° C. Is shown. As with the compressive modulus shown in Table 3, the storage modulus (E ') of the mixed polymer foams of Tests 2-5 is lower than the storage modulus (E') of the foams consisting solely of low density polyethylene of Test 1 over the entire temperature range. .

Test No. Storage modulus (E ') Tan δ 0 ℃ 20 ℃ 40 ℃ 0 ℃ 20 ℃ 40 ℃ One 1190 647 403 0.31 0.15 0.14 2 1080 549 158 0.15 0.20 0.16 3 962 475 275 0.15 0.17 0.16 4 772 394 228 0.16 0.18 0.16 5 894 484 281 0.16 0.18 0.17

In Table 4, Test 1 is a comparative example, the storage modulus (E ') is the value measured at 50 Hz oscillation speed at a given temperature in kPa, and Tan δ (tangent delta) is the loss modulus (E "). It is the ratio between and the storage modulus of elasticity (E '), which shows the damping performance against the impact of this foam.

As shown in FIG. 3 and Table 4, all mixed polymer foams exhibit higher tan delta values than foams consisting solely of low density branched polyethylene in the critical service temperature range of about 20-40 ° C. Therefore, it can be seen that the mixed polymer foam has improved damping performance than a foam composed of only low density side chain polyethylene. Here, the damping properties of the foams comprising the SIBS resin (tests 4 and 5) are assumed to originate from the SIBS resin. Moreover, it is surprising that polybutene-1 resin contributes to damping, which is unexpected from the physical properties of polybutene-1 resin. In the temperature range of about 5 ~ 35 ℃, it can be seen that the foam using the polybutene-1 copolymer is superior in the damping performance than the foam produced using the SIBS resin.

The polyolefin foam having improved physical properties according to the present invention can be foamed by a convenient process such as an extrusion process, but also has excellent flexibility, heat resistance, creep resistance, and damping performance. And, even when used as a floor cushioning material has the advantage that less deformation occurs.

Claims (7)

40 to 95% by weight of the expandable polyolefin resin, Including 5-60% by weight of characteristic variation resin, Wherein the property variant resin is at least one resin selected from the group consisting of polybutene-1 resin and styrene-olefin block copolymers, The polyolefin foam is a polyolefin foam, characterized in that the density of 9 ~ 100kg / m ³ . The method of claim 1, The polyolefin foam is a polyolefin foam, characterized in that the density of 15 ~ 50kg / m ³ . The method of claim 1, The expandable polyolefin resin is a low density side chain polyethylene resin, characterized in that the polyolefin foam. The method of claim 1, Wherein said polybutene-1 resin is at least one resin selected from the group consisting of polybutene-1 homopolymers and copolymers of butene-1 and other olefins. The method of claim 1, Wherein said styrene-olefin block copolymer is a styrene-isobutylene block copolymer. The method of claim 1, A nucleating agent, a foaming agent and a dimensional stabilizer are further added to the mixture which mixed the said foamable polyolefin resin and the said characteristic variation resin, The polyolefin foam characterized by the above-mentioned. The method of claim 1, The polyolefin foam is polyolefin foam, characterized in that produced by the extrusion process.

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