KR101263701B1 - Composition for an refrigerator gasket - Google Patents

Abstract

PURPOSE: A composition for a refrigerator gasket is provided to offer a refrigerator gasket having excellent compressing workability, surface properties, a shape maintaining property, and corner adhesion. CONSTITUTION: A composition for a refrigerator gasket comprises: an olefin block copolymer having at least over 100deg.C of melting point; and a blend of thermoplastic polyurethane as a polymer substrate. A melt index(190deg.C, 5kg) of the polymer substrate is 0.01-50g/10minutes, and the content of the thermoplastic polyurethane in the polymer substrate is 10-75wt%. The polymer substrate also comprises a styrene block copolymer. The thermoplastic polyurethane is one kind selected in a group comprising ester group TPU, ether group TPU, lactone group TPU, and butadiene group TPU.

Description

Composition for an refrigerator gasket

The technology disclosed herein relates to a composition for a refrigerator gasket.

Currently, the refrigerator gasket is profile extrusion of a composition including additives such as fillers and stabilizers in a soft vinyl chloride resin (PVC), and at this time, the rubber is mixed with a ferrite inside the gasket to extrude and magnetize. It is made by inserting the rubber strip of the made strip shape and heat-sealed to a predetermined length.

The vinyl chloride resin may generate dioxin upon incineration, and the plasticizer used to process the vinyl chloride resin has a problem when used in a product having high contact potential with food as an environmental hormone component. Therefore, Korean Patent Publication No. 2003-0042229 and Japanese Laid-Open Patent Publication No. 2000-017142 have been trying to substitute other materials for the manufacture of refrigerator gaskets instead of vinyl chloride.

However, in the case of other resins except vinyl chloride resin, release extrusion is difficult, elasticity is not maintained for a long time, and there are problems such as insufficient durability and surface adhesiveness, which makes it difficult to replace vinyl chloride resin in the refrigerator gasket field.

According to one aspect of the technology disclosed herein, the melting point of the polymer substrate includes a olefin block copolymer having a melting point of at least 100 ℃ or more, and a thermoplastic polyurethane, wherein the melt index (190 ℃, 5kg) of the polymer substrate is 0.01 to A composition for a refrigerator gasket, which is 50 g / 10 minutes, is provided.

According to another aspect of the technology disclosed herein, a blend of an olefin block copolymer, and a thermoplastic polyurethane as a polymer substrate, wherein the melt index of the polymer substrate (190 ℃, 5kg) is 0.01 to 50g / 10 minutes, Refrigerator gaskets with Shore A hardness of 60 to 80 are provided.

Hereinafter, the technique disclosed in the present specification will be described in more detail.

As described above, it is possible to release extrusion as a gasket material of the refrigerator and have a hardness of Shore A 60 to 80. As a soft material, it is difficult to find an alternative material except PVC. As a soft material for use in a refrigerator gasket, for example, when an ethylene copolymer or a thermoplastic rubber is used, there are difficulties as follows. If a soft material of Shore A 60 to 80 is used, the melting point is low, and the extrusion process is difficult due to the warpage of the product due to the slow speed of solidification after exiting the die during extrusion. On the other hand, when a material capable of extruding due to its high melting point is used, the hardness is too high, so that softeners such as process oils for reducing the hardness are mixed. At this time, the elastic loss of the product due to the softener and the softener leak out to the surface of the product and the product becomes sticky, and the adhesiveness is deteriorated when the corner is melt-bonded. Many side effects were difficult to commercialize.

Therefore, according to the technology disclosed herein, a novel composition for a refrigerator gasket is provided. The composition for a refrigerator gasket disclosed herein may include a blend of an olefin block copolymer (OCC) and a thermoplastic polyurethane (TPU) as a polymer substrate.

As used herein, the term " olefin block copolymer "generally refers to a block copolymer of a polymer comprising ethylene or an alpha -olefin having two or more carbon atoms with propylene. The α-olefin is an olefin having 2 or more carbon atoms having a double bond at the terminal.

Preferably, ethylene or propylene makes up the major mole fraction of the total polymer, ie ethylene or propylene makes up about 50 mol% or more of the total polymer. More preferably, ethylene or propylene comprises at least about 60 mol%, at least about 70 mol%, or at least about 80 mol% and the substantial remainder of the total polymer is preferably an α-olefin having at least 3 carbon atoms One or more other comonomers. For example, for ethylene / octene copolymers, preferred compositions have an ethylene content of at least about 80 mole percent of the total polymer, and an octene content of about 10 to about 15 mole percent, preferably about 15 to about 20 mole percent of the total polymer. It includes.

The olefin block copolymer (olefin block copolymer, OBC) is a multiblock copolymer. They are preferably end-to-end relative to polymers comprising two or more chemically distinct zones or segments (referred to as "blocks") joined in a linear manner, ie polymerized ethylene- or propylene-functional groups rather than pendant or grafted A polymer comprising chemically separated units which are terminally bound.

The olefin block copolymer (OBC) means ethylene / α-olefin multiblock copolymer or propylene / α-olefin multiblock copolymer. The olefin block copolymer comprises ethylene or propylene in the form of polymerized one or more copolymerizable α-olefin comonomers, and multiblock copolymer having a plurality of blocks or segments of two or more polymerized monomer units having different chemical or physical properties. It is characterized by a chain. The content of olefin and? -Olefin in the OBC is the same as described for the ORC.

In some embodiments, the multi-block copolymer can be represented by the following formula:

(AB) n

In the formula, n is an integer of 1 or more, preferably more than 1, such as 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, or more ; "A" represents a hard block or segment; "B" represents a soft block or segment. Preferably, A and B are connected in a linear fashion rather than in a branched or star fashion. By "hard" segment is meant a block of polymerized units in which ethylene or propylene is present in an amount of at least 95 weight percent, in some embodiments at least 98 weight percent, in some embodiments. That is, the comonomer content in the hard segment is, in some embodiments, 5 wt% or less, and in other embodiments, 2 wt% or less of the total weight of the hard segment. In some embodiments, the rigid segments consist of all or substantially all of ethylene or propylene. By contrast, a "soft" segment is a segment of polymerized units wherein the comonomer content is at least 5 wt%, in various embodiments greater than or equal to 8 wt%, at least 10 wt%, or at least 15 wt% of the total weight of the soft segment in some embodiments Block. In some embodiments, the comonomer content in the soft segment is greater than or equal to 20 wt%, greater than 25 wt%, greater than 30 wt%, greater than 35 wt%, greater than 40 wt%, greater than 45 wt%, greater than 50 wt% Or more, or 60 wt% or more.

In one embodiment, the olefin block copolymer may have a density of 0.85 to 0.91 g / cc, or 0.86 to 0.88 g / cc.

In one embodiment, the olefin block copolymer has a melt index (MI) as measured by ASTM D1238 (190 ° C., 2.16 kg) of 0.01 to 30 g / 10 minutes, or 0.01 to 20 g / 10 minutes, or 0.1 to 10 g / 10 minutes, or 0.1 to 5.0 g / 10 minutes, or 0.1 to 3.0 g / 10 minutes, or 0.1 to 1.0 g / 10 minutes, or 0.3 to 0.6 g / 10 minutes.

An example of the olefin block copolymer is Dow Chemical's Infuse. The OBC used in the technology disclosed herein has a high melting point of at least 100 ° C. or higher, and thus release extrusion can be performed. However, most of the OBCs capable of release extrusion are difficult to use in refrigerator gaskets due to their low elasticity. Therefore, it is necessary to blend other materials to satisfy the low hardness and viscosity of the molten resin required for release extrusion for use in refrigerator gaskets. In addition, in order for the OBC to be used in the refrigerator gasket, it is preferable that the airtightness of the gasket is maintained even after opening and closing operations of tens of thousands to several hundred thousand times. This requires considerable high elasticity. In order to solve this problem, the styrene block copolymer (SBC) may be blended, but when blending more than a predetermined amount to give elasticity, the surface roughness may be severe and adhesion may be reduced when the refrigerator is mounted. Thus, according to the compositions disclosed herein, thermoplastic polyurethane (TPU) is blended with OBC to improve low hardness, high elasticity, high viscosity properties during extrusion, as well as melt adhesion and surface properties.

TPU is prepared by the reaction of organic diisocyanates, polymeric diols and chain extenders, and has a unique elasticity due to the phase separation between the hard and soft segments. Any TPU known in the art may be used in the compositions disclosed herein. For example, the TPU may be one selected from the group consisting of ester TPU, ether TPU, lactone TPU, and butadiene TPU.

The formulation of the TPU used in the composition is not particularly limited as long as it is thermoplastic, and is substantially prepared from a bifunctional component, and contains a small amount of over two functional components (eg, chain extenders such as glycerin, trimethylolpropane). May be used. Preferred TPUs are polymers made from mixtures comprising organic diisocyanates, at least one polymeric diol and at least one difunctional chain extender.

The diisocyanate which is a raw material of the TPU required for the present composition includes an aromatic, aliphatic and alicyclic diisocyanate and a combination of two or more of these compounds. Polymeric diols that can be used include those conventionally used in the art in the preparation of TPU elastomers. The polymeric diols are responsible for the formation of soft segments of the resulting polymer, preferably having a number average molecular weight of 200 to 10,000 g / mol, preferably 400 to 4,000 g / mol, more preferably 500 to 3,000 g / mol Is in range. Examples of polymeric diols include polyether diols, polyester diols, hydroxy terminated polycarbonates, hydroxy terminated polybutadienes, hydroxy terminated polybutadiene-acrylonitrile copolymers, dialkyl siloxanes and alkylene jades Seeds and the like. Chain extenders can be aliphatic, cycloaliphatic or aromatic and are exemplified by diols, diamines and amino alcohols.

 In one embodiment, the polyurethane has a density of at least 0.90 g / cc, preferably at least 0.95 g / cc, more preferably at least 1.00 g / cc. In another embodiment, the polyurethane has a density of 1.30 g / cc or less, preferably 1.25 g / cc or less, more preferably 1.20 g / cc or less. In another embodiment, the polyurethane has a density of 0.90 g / cc to 1.30 g / cc, preferably 0.95 g / cc to 1.25 g / cc, more preferably 1.00 g / cc to 1.20 g / cc.

In one embodiment, the polyurethane has a melt index of at least 0.1 g / 10 minutes, preferably at least 0.5 g / 10 minutes, more preferably at least 1 g / 10 minutes (ASTM D-1238-04, 190 ° C., 8.7 measured by kg). In another embodiment, the polyurethane has a melt index of 100 g / 10 min or less, preferably 50 g / 10 min or less, more preferably 20 g / 10 min or less (ASTM D-1238-04, 190 ° C., Measured by 8.7 kg). In another embodiment, the polyurethane has a melt index of 0.1 g / 10 minutes to 100 g / 10 minutes, preferably 0.5 g / 10 minutes to 50 g / 10 minutes, more preferably 1 g / 10 minutes to 20 g / 10 min (as measured by ASTM D-1238-04, 190 ° C., 8.7 kg).

In the composition for refrigerator gasket, the content of TPU in the polymer substrate including OBC and TPU is 10% by weight or more, preferably 20% by weight or more, 75% by weight or less, preferably 70% by weight or less, more preferably Is preferably at most 60% by weight, even more preferably at most 50% by weight. In one embodiment, the TPU may be included in 10 to 75% by weight. If the TPU is less than 10% by weight, the surface smoothness of the extrudate may be insufficient, and if it is more than 75% by weight, the release extrudability may be poor due to the decrease in the melt viscosity.

Compatibilizers may be further included to increase the miscibility of the OBC and TPU. Examples of suitable compatibilizers include amine modified SBBS (amine modified styrene-butadiene / butylene-styrene, ex: Tuftec MP-10 from Asahi Kasei) or maleic anhydride (MAH) modified EPDM.

In order to improve the workability of the final mixture, a lubricant such as stearic acid, ethylene bis stearamide, or a mixture of silica (SiO ₂ ) is used to further lower the MI of the mixture or to increase the viscosity. Fillers such as, MgCO ₃ , CaCO ₃ , Talc, Al (OH) ₃ , Mg (OH) _2, and the like.

The polymer substrate may further include an ethylene copolymer (eg, EVA, EEA, EMA, EBA, ENMMA, POE, etc.) or a thermoplastic rubber (eg, 12-PB, SBC, TPEE, etc.) in addition to OBC and TPU. Preferably, the polymer substrate may further include a styrene block copolymer (SBC) in addition to the OBC and the TPU. The composition for a refrigerator gasket may include, for example, an ethylene-octene block copolymer and a styrene-ethylene-butylene-styrene block copolymer as a polymer substrate. By appropriate mixing of SBC and TPU, a gasket for a refrigerator having excellent elasticity and excellent surface smoothness can be obtained.

Alternatively, small amounts of olefin random copolymers (ORC) or low density polyethylene (LDPE) may be included to lower the price.

The MI (190 ° C., 5 kg) of the final mixed composition is 0.01 to 50.0 g / 10 minutes, preferably 1.0 to 30.0 g / 10 minutes, more preferably 1.0 to 15.0 g / 10 minutes, even more preferably 1.0 to 10.0 g / 10 min is preferred. If the MI (190 ℃, 5kg) of the final mixed composition is less than 0.01g / 10 minutes extruded too high pressure on the extruder high risk of damage to the machine and the extrusion amount is so small that it takes too long time to produce the desired product If the MI (190 ℃ 5kg) is more than 50g / 10 minutes, the viscosity of the mixture exiting the die of the extruder is low, the product is warped, the desired shape can not be obtained.

The refrigerator gasket may be manufactured by release extrusion of the composition for a refrigerator gasket disclosed herein. Mixing of the composition for a refrigerator gasket may be performed in a manner known to those skilled in the art. For example, a mixer such as a Banbury mixer or booth kneader may be used. It is also possible to use conventional single or twin screw extruders for extrusion.

 Refrigerator gasket manufactured using the composition for a refrigerator gasket disclosed in the present disclosure has excellent extrusion workability, excellent elasticity, excellent corner adhesiveness, no surface stickiness, and excellent surface smoothness.

In one embodiment, the polymer base comprises a blend of an olefin block copolymer and a thermoplastic polyurethane, wherein the polymer has a melt index (190 ° C., 5 kg) of from 0.01 to 50 g / 10 minutes and a Shore A hardness of 60 to An 80-person refrigerator gasket is provided.

At this time, the olefin block copolymer is preferably a melting point of 100 ℃ or more. In a preferred embodiment, the olefin block copolymer may be ethylene or a copolymer of propylene and octene.

A rubber magnet may be included in the body of the refrigerator gasket. The rubber magnet may be a strip made by extruding and magnetizing a mixture of magnetic powder and rubber.

In order to secure proper physical properties such as elasticity and corner adhesion, the content of TPU in the polymer substrate is 10% by weight or more, preferably 20% by weight or more, 75% by weight or less, preferably 70% by weight or less, more preferably. Preferably at most 60% by weight, even more preferably at most 50% by weight.

Hereinafter, the technology disclosed herein will be described in more detail with reference to examples, but the spirit of the disclosed technology is not limited by the present embodiment.

<Examples>

The following raw materials were released and extruded to prepare a refrigerator gasket and evaluated for performance.

ORC-1: Olefin Random Copolymer (Ethylene-Butene), Density: 0.875 g / cc, MI (190 ° C, 2.15 kg): 2.0

OBC-1: Olefin Block Copolymer (Ethylene-Octene), Density: 0.870 g / cc, MI (190 ° C, 2.15 kg): 3.0

EVA-1: Ethylene Vinylacetate (VA 26%), MI (190 ° C 2.15 kg): 2.5

SEBS-1: styrene ethylene butylene styrene (Styrene Ethylene Buthylene Styrene, Styrene 30%), MI (190 ℃, 2.15 kg): 4.0

TPU-1: ester-based TPU (Ester based TPU, Dongsung Hichem Grade 5080A)

TPU-2: Ether based TPU (Dongsung Hichem Grade 6180A)

TPU-3: lactone-based TPU (Lactone based TPU, Dongsung Hichem Grade 4080A)

(Performance evaluation)

1) Extrusion workability: After adjusting the cylinder temperature to 170 ° C. in an extruder in which a cylinder diameter of 100 mm and an L / D of 36: 1 are combined with a die of a refrigerator gasket shape, extrude the mixtures of Comparative Examples and Examples. Immediately after the extrudate comes out through the die, it passes through a chamber equipped with a freezer (set at a temperature of 100 ℃ and a pass time of 20 seconds) to obtain the desired shape and comprehensively judge the extrudeability.

2) Surface stickiness: touch test

3) Elasticity: The mixture was placed in a mold having a thickness of 2 mm, heated under pressure at 200 ° C. for 5 minutes, and cooled in a cold press for 5 minutes to obtain a mixture specimen having a thickness of 2 mm. Cut the mixture specimen into 2mm width and 100mm length, tape both ends of the specimen and make it round, leave it for 10 minutes, cut the tape, measure the time for the specimen to return to its original straight shape, and make it short. From A, B, C, D, E.

4) Formability: Cut the 2mm thick specimen into 10mm wide and 100mm long, hang it on a Demattia flexure tester, make 200,000 bends, and change its shape according to the degree of deformation of the original specimen (planar). Rated, C, D, and E.

5) Corner adhesiveness: Make the specimens 5mm thick and 100mm long, and contact the two specimens with both surfaces of the double-sided heater with a temperature of 250 ℃ to melt the surface, remove the heaters, and stick the specimens together for 1 second, 2 seconds, 3 A second, 4 second, and 5 second release was followed by grading the grades A, B, C, D, and E, depending on how quickly the adhesive was fixed.

6) Surface smoothness: The surface smoothness of the specimens was visually inspected and graded A, B, C, D, and E in order of smoothness.

The results are shown in Table 1 below.

[Table 1]

A: Excellent, B: Excellent, C: Normal, D: Poor, E: Poor

Referring to Table 1, as described in Examples 1 to 4, the refrigerator gasket manufactured by releasing and extruding a composition for a refrigerator gasket using OBC and TPU as the polymer substrate at the same time has excellent compression workability, but has surface characteristics, shape retention, It has excellent corner adhesiveness and has very suitable properties as a gasket. On the other hand, Comparative Example 5 generally exhibited excellent physical properties but lacked surface smoothness.

On the other hand, even if the blend of OBC and TPU as a polymer substrate, when the melt index (190 ℃, 5kg) exceeds 50g / 10 minutes as in Comparative Example 6 it can be seen that the extrusion workability is poor.

From the above, various embodiments of the disclosed technology have been described for the purposes of illustration, and it will be understood that there are various possible variations without departing from the scope and spirit of the disclosed technology. And, the various embodiments disclosed are not intended to limit the spirit of the disclosed technology, and the true spirit and scope will be set forth in the claims below.

Claims (13)

The polymer base includes a olefin block copolymer having a melting point of at least 100 ° C. or more, and a blend of thermoplastic polyurethane,
Melt index (190 ℃, 5kg) of the polymer substrate is 0.01 to 50g / 10 minutes,
A composition for a refrigerator gasket, wherein the content of the thermoplastic polyurethane in the polymer substrate is 10 to 75% by weight. delete delete The method according to claim 1,
The polymer substrate is a composition for a refrigerator gasket further comprising a styrene block copolymer. The method according to claim 1,
The thermoplastic polyurethane is a refrigerator gasket composition which is one selected from the group consisting of ester-based TPU, ether-based TPU, lactone-based TPU, and butadiene-based TPU. The method according to claim 1,
Melting index (190 ℃, 5kg) of the polymer substrate is a composition for refrigerator gaskets 1 to 10g / 10 minutes. The polymer base includes a olefin block copolymer having a melting point of at least 100 ° C. or more, and a blend of thermoplastic polyurethane,
Melt index (190 ℃, 5kg) of the polymer substrate is 0.01 to 50g / 10 minutes,
A composition for a refrigerator gasket further comprising an amine-modified SBBS or maleic anhydride (MAH) -modified EPDM as a compatibilizer. The polymer base includes a olefin block copolymer having a melting point of at least 100 ° C. or more, and a blend of thermoplastic polyurethane,
Melt index (190 ℃, 5kg) of the polymer substrate is 0.01 to 50g / 10 minutes,
Refrigerator gasket composition further comprises an ethylene copolymer or a thermoplastic rubber in the polymer substrate. A refrigerator gasket comprising an olefin block copolymer and a blend of thermoplastic polyurethane as a polymer substrate,
Melt index (190 ℃, 5kg) of the polymer substrate is 0.01 to 50g / 10 minutes,
A refrigerator gasket including a rubber magnet inside the refrigerator gasket body. 10. The method of claim 9,
A refrigerator gasket having a Shore A hardness of 60 to 90 on the polymer substrate. The method of claim 10,
The olefin block copolymer has a melting point of 100 ℃ or more refrigerator gasket. The method of claim 10,
The olefin block copolymer is a refrigerator gasket is a copolymer of ethylene or propylene and octene. Olefin block copolymers, and blends of thermoplastic polyurethanes as polymer substrates,
Melt index of the polymer substrate (190 ℃, 5kg) is 0.01 to 50g / 10 minutes, Shore A hardness is 60 to 80,
Refrigerator gasket having a content of the thermoplastic polyurethane in the polymer substrate of 10 to 75% by weight.