KR101808032B1 - Polyurethane resin composition for microporous foam sheet as emi gasket material - Google Patents

Abstract

The present invention relates to a polyurethane resin composition for a microporous foam sheet for an EMI gasket material. According to an embodiment of the present invention, the polyurethane resin composition for the microporous foam sheet for the EMI gasket material comprises a polyurethane prepolymer curing agent, and a base. The polyurethane resin composition for the microporous foam sheet for the EMI gasket material according to the present invention can improve mechanical properties of a foam sheet thin-film, and improve conductivity due to inclusion of carbon nanotubes.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyurethane resin composition for a micro-porous foam sheet for an EMI gasket material and a polyurethane resin composition for an EMI gasket material.

The present invention relates to a polyurethane resin composition for a microporous foam sheet for an EMI gasket material, and more particularly, to a polyurethane resin composition for a microporous foam sheet for an EMI gasket material, The thickness of 120 μm or less is applied to the gap formed between the parts and the case integrated in the case of the electronic device by producing the foamed foam sheet. Therefore, it is possible to improve the EMI in the shock absorption, sealing and electromagnetic wave shielding To a polyurethane resin composition for a microporous foam sheet for a gasket material.

In the present invention, electromagnetic interference (EMI) is interpreted as electromagnetic interference and electromagnetic interference, and means that electromagnetic waves radiated or conducted directly from electrical and electronic devices cause interference to electromagnetic receiving functions of other devices. Methods of shielding or suppressing unnecessary noise causing electromagnetic interference (EMI) include grounding, laying, filtering, and shielding, among which shielding and grounding Grounding is the most fundamental way to prevent damage to circuits or devices that are affected by noise.

In particular, smartphone technology has been limited to some chips such as communication chips in the past. However, EMI shielding technology will be expanded to include application process (AP), modem chip, radio frequency (RF), connectivity (wireless LAN, Bluetooth) , And the EMI shielding process is expected to increase in parts for wearable and Internet (IoT) devices as well as smartphones, and the equipment market is expected to grow in the future.

It is required to elaborate various components and to minimize the size according to the trend of miniaturization and thinning of electronic devices. Also, it is required to minimize the thickness of the gasket for sealing between the internal parts and the case, Development of materials having physical properties is required. In order to cope with products having such various materials and gaps, mechanical properties such as impact absorbability and compressibility must be excellent and conductivity must be realized at a minimum thickness.

Generally, the sealability of the sealing member is evaluated as to whether or not the sealing member is easily deformed by the load. Therefore, when the sealing member is highly compressed, an olefin type foam such as a flexible polyurethane foam, a polyethylene foam or a polypropylene foam, or a rubber foam is used in order to have a proper sealing property.

In recent years, research on the thinning of gaskets due to the miniaturization of electronic devices is actively under way. In the field of urethane materials development, various polyols have been developed, but two-component poly In the case of the urethane foam sheet, it is known that the buffer retention due to use for a long time is weakened, the thickness deviation is large, and it is difficult to form a thin film.

Accordingly, a lot of studies have been made to provide a high compressibility and a high resilience by producing a foam sheet having a uniform thickness by applying a polyfunctional polyol. However, when a multi-functional polyol is simply formulated to form a thin film sheet As the content of the functional group polyol increases more than a certain amount, the reaction rate is slowed, and tensile strength, elongation and elastic modulus are lowered. In order to develop a microcellular foam sheet for highly resilient EMI gasket materials, It is essential to improve flowability, workability, mechanical properties, elasticity and permanent compression reduction.

The thinner the sheet is, the less the strength of the sheet itself is reduced and the processability is lowered. When the thickness of the sheet is reduced, it can be improved by controlling the content of the polyol or by treating with a reinforcing agent. Application is also known in an effective way to improve the strength and conductivity of the sheet.

However, carbon nanotubes are entangled because they are aggregated into bundles by a strong van der waals force. If the carbon nanotube is in such a state in the matrix, it can not exhibit its inherent characteristics and can not provide conductivity substantially, which may cause deterioration of mechanical properties. Therefore, it is necessary to uniformly disperse the carbon nanotubes in the matrix, that is, the polyurethane resin, in order to obtain a uniform strength and electric conductivity by the carbon nanotubes.

Various methods for dispersing carbon nanotubes have been known so far. However, in order to effectively disperse carbon nanotubes, aggregation of carbon nanotubes must be completely canceled and strong re-aggregation of carbon nanotubes must be suppressed. Therefore, in the present invention, functional groups such as -COOH and -OH are formed on the surfaces of carbon nanotubes through acid treatment for increasing dispersibility and strength in a urethane matrix, and they are first reacted with isocyanate to form a carbon nanotube isocyanate composite prepolymer And then reacting it with a polyol to prepare a polyurethane resin.

As an example, a technique for imparting functional groups such as --COOH and --OH to the surface of a carbon nanotube is disclosed in Korean Patent Publication No. 10-0853127 (registered on Aug. 13, 2008), Registered Patent Publication No. 10-1065741 Registration on September 09, 2011).

In the prior art relating to the gasket material polyurethane foam, in accordance with the present invention, a curable low density polyurethane foam is produced in the process of Japanese Patent Application Laid-Open No. 10-2007-0018260 (Applicant: Rogers Inoak Co., A step of foaming a composition for forming reactive polyurethane comprising an isocyanate-containing component, an active hydrogen-containing component which reacts with the isocyanate-containing component, a foaming agent, a surfactant and a catalyst system; Casting the foamed reactive polyurethane forming composition onto a first carrier, placing a second carrier on a side of the casted foam body facing the first carrier; Bubbling the foam body with the second carrier in place; And curing the blown foam body to form a polyurethane foam layer having a density of 50 to 400 kg / m ³ and a thickness of 0.3 to 13 mm, wherein the catalyst system is provided for retarding the curing of the foam And is described as useful as a sealing member.

In addition, Japanese Unexamined Patent Application Publication No. 10-2005-0008347 (filed by Hepce Chem Co., Ltd.) discloses a porous polyurethane body containing a urethane polyol prepolymer which is easy to store and handle and a method for producing the same. The urethane polyol prepolymer has a urethane group in the main chain of the polymer in a semi-solid state or a solid state at room temperature, and contains at least two hydroxyl groups as functional groups. The method comprises heating and melting the urethane polyol prepolymer, adding an isocyanate compound containing an isocyanate group (-NCO) reacting with the hydroxyl group of the urethane polyol prepolymer, and a urethane curing catalyst, and stirring the mixture at a high speed to form a mechanical foam. And cooling or compressing the formed mechanical foams at room temperature to form a porous polyurethane body. The porous polyurethane formed by the above-mentioned method is obtained by melt-agitation without using a solvent or a dryer, and has excellent chemical and physical properties.

In addition, 0.1 to 5 parts by weight of a catalyst and 0.5 to 4 parts by weight of a chain extender are added to 100 parts by weight of the polyol and 100 parts by weight of the polyol of Patent Application No. 10-2009-0058373 (Applicant: Hyundai Motor Co., And 2 to 35 parts by weight of a foaming agent, and 20 to 60 parts by weight of an isocyanate. The low-density polyurethane foam composition is excellent in physical properties such as light weight, high hardness and high durability, It is an environmentally friendly material that is relatively inexpensive to manufacture than conventional polyurethane foam compositions and has an odor-inducing effect, and is therefore well suited for use in bedding materials, automobile interior materials, and automobile seat pads.

In addition, EP-B-10-2013-0115271 (Dow Global Technologies, Inc., USA) discloses blends of polyols and elastomeric flexible polyurethanes that function well in vehicle noise and vibration absorbing products made from isocyanates Wherein the blend of polyols each have 1200 to 3000 hydroxyl equivalents, 70% or more of primary hydroxyl groups, 5 to 80% by weight of ethylene oxide capped polypropylene oxide is pore-bifunctional, 0.5 to 20% by weight of ethylene oxide-capped polypropylene oxide having a pore-curing functionality of 4 or more and a balance of 1.5% by weight or more of ethylene oxide-capped polypropylene oxide, And has a hydroxyl number in the range of from 15 to 200, wherein said autocatalytic Wherein the lanolide compound comprises a mixture of an autocatalytic polyol having one or more tertiary amine groups and a low unsaturation polyol having a functionality of at least 2, a hydroxyl equivalent of 1800 to 2800, and a total unsaturation of 0.06 meq / g or less will be.

In addition, in JP-A-10-2012-0021697 (filed by Youngbo Chemical Co., Ltd.), a base resin composed of an ethylene-vinyl acetate (EVA) copolymer resin or a polyolefin-based copolymer resin, a crosslinking agent, a foaming agent, (CNT), a mixture preparation process for preparing a conductive foamed foam mixture containing a conductive carbon nanotube (CNT) composition, an extrusion process for extruding a conductive foamed foam mixture into a matrix, and a preparation process for the mixture (Or an electron beam cross-linking step and a foaming step) of chemically cross-linking as a cross-linking agent, and foaming as a foaming furnace, and a conductive foamed foam produced using the carbon nanotube- Technology.

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In addition, in the above-mentioned Japanese Patent Application No. 10-1182723 (Applicant: Korean Footwear Leather Research Institute), carbon nanotubes including a step of mixing a carbon nanotube and a polyol and a step of dispersing the carbon nanotube in the polyol are uniform Wherein the dispersing step comprises a step of subjecting the mixture to a ball mill treatment, a step of treating the mixture with an ultrasonic treatment, and a step of subjecting the mixture to a roll mill treatment The method comprising the steps of: The present invention also relates to a conductive polyurethane resin composite having uniformly dispersed carbon nanotubes comprising the step of reacting a polyol composition dispersed with carbon nanotubes as described above with a diisocyanate compound in an organic solvent to form a polyurethane resin Of the present invention.

The present invention relates to a polyurethane resin composition using a surface-treated carbon nanotube and a polyfunctional polyol, wherein the surface-treated carbon nanotube is reacted with an isocyanate to prepare a prepolymerized poly To a polyurethane resin composition for a microporous foam sheet for an EMI gasket material having improved dispersibility, mechanical properties, resilience and conductivity.

Korean Patent Publication No. 10-2007-0018260 (published on February 14, 2007) Korean Patent Publication No. 10-2005-0008347 (published on January 21, 2005) Korean Patent Laid-Open No. 10-2009-0058373 (Publication date: 2009. 06. 09) Korean Patent Publication No. 10-2013-0115271 (Publication date: October 21, 2013) Korean Patent Publication No. 10-2012-0021697 (published on March 03, 2012) Korean Patent Registration No. 10-1182723 (Published on Mar. 13, 2012)

It is an object of the present invention to provide a polyurethane prepolymer hardener having a high molecular weight and a low NCO content to which carbon nanotubes are applied in order to improve the elasticity when formed into a sheet having a low viscosity while containing a poly-caprolactone polyol, polypropylene glycol, The foamed sheet of the present invention is superior in terms of restoration, sheet strength and conductivity compared to conventional polyurethane foam sheets exhibiting a long and low compression loss ratio, so that shock absorption, sealing and electromagnetic shielding And to provide a polyurethane resin composition for a microporous foam sheet for a good EMI gasket material.

(A) 0.1 to 10 parts by weight of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.1 to 10 占 퐉, (b) an isocyanate 70 (D) 0 to 30 parts by weight of a polyether polyol having a hydroxyl value of 150 to 250 mg KOH / g, and (d) 0.1 parts by weight of a bismuth carboxylate catalyst. Urethane prepolymer hardener; And (e) 10 to 20 parts by weight of a polycaprolactone polyol having a hydroxyl group content of 93 to 560 mg KOH / g, (f) 45 to 70 parts by weight of a polypropylene glycol having a hydroxyl group content of 28 to 56 mg KOH / (I) 0.5 to 1.5 parts by weight of a nickel catalyst, (j) 0.5 to 3.0 parts by weight of a foam stabilizer, (i) 5 to 29 parts by weight of a polyfunctional polyol having a hydroxyl value of 448 mgKOH / g, And the like.

According to a preferred embodiment of the present invention, the carbon nanotube (a) used in the polyurethane prepolymer curing agent is surface treated with nitric acid (NH ₃ ) to adjust the hydroxyl value to 112 to 1,200 mgKOH / g, Carbon nanotubes are prepared from prepolymer of isocyanatized carbon nanotubes by reacting with isocyanate (b).

The isocyanatized carbon nanotubes are prepared in a molar ratio of 1: 2 to 1: 4 in the OH group of the carbon nanotubes having the hydroxyl value of the prepolymer and the NCO group of the diisocyanate, and the isocyanate- The polyol which undergoes a polymerization reaction with the prepolymer is characterized by being a polyfunctional group polyol (g).

The polyurethane prepolymer curing agent has an NCO content of 10 to 20% by weight and a viscosity of 400 to 1,500 cps / 25 ° C. Next, the polyurethane prepolymer curing agent and the base are mixed in a ratio of NCO / OH molar ratio of 0.8 to 1.2, and the viscosity is in the range of 500 to 2,000 cps / 25 ° C. When the organic solvent is not contained, %, A density of 0.3 to 0.6 g / cm 3, an average pore size of 10 to 30 탆, and a sheet strength of 4.5 to 7.2 kgf / cm 2, as a polyurethane resin composition.

The polyurethane resin composition for an EMI gasket material for an EMI gasket material of the present invention is characterized in that the isocyanatized carbon nanotubes directly participate in the polyurethane reaction to maximize the dispersibility with the carbon nanotubes and the bonding force with the resin, The mechanical properties of the sheet thin film are improved and the effect of improving the conductivity due to the inclusion of the carbon nanotubes can be obtained.

In addition, the polyurethane resin composition for a microcellular foam sheet for an EMI gasket material of the present invention uses a high-elasticity polyol and a polyfunctional-group polyol to have a low viscosity, a high molecular weight and a low NCO content, Compared to foam sheet exhibiting low permanent compression loss ratio, EMI shielding of more than 60%, sheet strength of more than 6kgf / cm2, and conductivity, and shock absorbing and sealing and electromagnetic wave shielding rate of 65dB or more even under a thin film of less than 0.12t / Shielding / Grounding Gasket material.

(A) 0.1 to 10 parts by weight of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.1 to 10 占 퐉, (b) an isocyanate 70 (D) 0 to 30 parts by weight of a polyether polyol having a hydroxyl value of 150 to 250 mg KOH / g, and (d) 0.1 parts by weight of a bismuth carboxylate catalyst. Urethane prepolymer hardener; And (e) 10 to 20 parts by weight of a polycaprolactone polyol having a hydroxyl group content of 93 to 560 mg KOH / g, (f) 45 to 70 parts by weight of a polypropylene glycol having a hydroxyl group content of 28 to 56 mg KOH / (I) 0.5 to 1.5 parts by weight of a nickel catalyst, (j) 0.5 to 3.0 parts by weight of a foam stabilizer, (i) 5 to 29 parts by weight of a polyfunctional polyol having a hydroxyl value of 448 mgKOH / g, And the like.

Hereinafter, the polyurethane resin composition according to the present invention will be described. However, it should be understood that the present invention is not limited to the polyurethane resin composition of the present invention, And does not imply that the technical idea and scope are not limited.

First, the polyurethane prepolymer curing agent of the present invention comprises (a) 0.1 to 10 parts by weight of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.1 to 10 μm, (b) 70 to 90 parts by weight of an isocyanate, 0 to 30 parts by weight of a polyether polyol having a hydroxyl group content of 250 mgKOH / g, and (d) 0.1 part by weight of a bismuth carboxylate catalyst.

The carbon nanotube (a) is used in a range of 0.1 to 10 parts by weight of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.1 to 10 占 퐉 in a polyurethane prepolymer curing agent, more preferably an average diameter of 1 to 50 nm Walled carbon nanotube having an average length of 0.1 to 5 μm and a purity of 95 wt% or more is used in an amount of about 0.1 to 4 parts by weight.

When the carbon nanotubes have an average diameter of less than 1 nm and an average length of less than 0.1 占 퐉, the size of the nanotubes is excessively small. As a result, the prepolymer curing agent or the resin after blending has high viscosity and poor dispersibility, And when the mean diameter is more than 50 nm and the average length is more than 10 탆, the processability of the carbon nanotubes to the compound liquid of the conductive foamed sheet, that is, the polyurethane resin composition for the microporous foam sheet deteriorates and the conductivity is not effectively expressed. Accordingly, the carbon nanotube content in the present invention is preferably in the range of 0.1 to 10 parts by weight based on the total weight of the curing agent. When the amount of the carbon nanotubes is too small, the final product does not exhibit sufficient mechanical strength and electrical conductivity, In many cases, it has been confirmed that uniform dispersion is not achieved and workability is degraded.

In the surface treatment step of carbon nanotubes which give functional groups such as -COOH and -OH on the surfaces of carbon nanotubes, 5 g of carbon nanotubes (CNT) are mixed with 100 g of 30 mol% nitric acid (NHO ₃ ) After the surface of the carbon nanotubes is activated by stirring for 2 to 24 hours at a temperature of ~ 90 ° C, the surface-treated carbon nanotubes are treated with distilled water and acetone or methyl ethyl ketone The mixture was filtered five times using a filter device, and after the pH was confirmed, it was judged whether or not to clean the carbon nanotube powder. The carbon nanotube powder was then dried in a drier at about 100 ° C. for 24 hours. At this time, it is possible to effectively produce isocyanatized carbon nanotubes in the next step by controlling the formation of -COOH and -OH through the peak of IR and controlling the hydroxyl value to 112 to 1,200 mgKOH / g.

When the surface of the carbon nanotubes is surface-treated as described above, the surface of the carbon nanotubes can be treated with a strong acid such as nitric acid, sulfuric acid or a mixture thereof. However, when sulfuric acid is used in comparison with nitric acid, It is difficult to control the reactivity by excessively introducing functional groups on the surface.

In order to obtain a stable polyurethane resin having a uniform molecular weight, the hydroxyl value of carbon nanotubes to be reacted with isocyanate should be controlled to 112 to 1,200 mgKOH / g. If the hydroxyl value is less than 112 mgKOH / g, the number of functional groups on the surface of the carbon nanotube is low and the reactivity with isocyanate is low. When the hydroxyl value is more than 1,200 mgKOH / g, a large number of isocyanates bind to the surface of the carbon nanotube, do. In the present invention, the hydroxyl value of the surface of the cleaned and dried carbon nanotubes is measured. When the hydroxyl value is insufficient, the concentration of nitric acid (NH ₃ ), the reaction temperature, and the reaction time are controlled to obtain the hydroxyl value So that the carbon nanotubes activated at only a part of the surface are used.

Next, the surface-treated carbon nanotube is reacted with isocyanate to prepare an isocyanatized prepolymer (prepolymer). In the present invention, a carbon nanotube surface-treated with a hydroxyl value -OH, and -COOH group with a liquid isocyanate to produce an isocyanatized carbon nanotube urethane monomer and / or an oligomer-type prepolymer.

On the other hand, when the polyurethane is processed into a thin film foam sheet, viscosity and fluidity of the resin are important factors. If the viscosity is too high, the defective rate of the foam sheet becomes high and the control of the thickness and bubbles becomes difficult. On the other hand, when the viscosity is too low, a foam sheet of sufficient thickness is not formed and shrinkage and form become unstable . A typical foam sheet is prepared by mixing an isocyanate and a polyol with a catalyst and a foam stabilizer and then mixing the foaming agent at a predetermined mixing ratio. In this case, when commercially available isocyanate or a prepolymer using the isocyanate is used, the NCO% is determined There is a limitation in adjusting the characteristics of such pores because excessive reaction occurs to form micropores of 20 탆 or less.

Generally, when a flexible thin film foam sheet is produced, having a low NCO% is advantageous in controlling the size and thickness of the pores, but isocyanate prepolymer having a low NCO% has high viscosity, which makes it difficult to process the thin film foam sheet . On the other hand, when the NCO content and the viscosity are adjusted by simply using a low molecular weight polyol, the hardness of the sheet becomes high and a sufficient sealing property can not be exhibited.

As a result of repeated trial and error, it has been found that the commercially produced methylenediphenyl diisocyanate product has a high NCO content of about 30 to 35 wt% and is difficult to form fine pores due to its rapid reactivity The present inventors have found that there is a limit to the production of microporous foam sheets. Thus, using isocyanates, carbon nanotubes, and polyether polyols, it is possible to obtain a microporous foam sheet having a viscosity of 400 to 1,500 cps / A polyurethane prepolymer having an NCO content of% was applied.

The method for producing the isocyanate-modified carbon nanotube prepolymer by reacting the carbon nanotube having the hydroxyl value adjusted with isocyanate is not particularly limited to the specific reaction conditions, but the prepolymer may be prepared by reacting isocyanate with carbon nanotubes In the presence or absence of a catalyst or with the addition of an inhibitor, at a temperature of 50 to 90 DEG C for 2 to 24 hours.

The molar ratio of the OH group of the carbon nanotube to the NCO group of the diisocyanate is controlled to be 1: 2 to 1: 6 in the step of preparing the prepolymer of the isocyanatized carbon nanotube, The ratio of 1: 2 to 1: 4 is appropriate. At this time, (b) a bismuth carboxylate catalyst is added to the polyurethane prepolymer curing agent at a ratio of 0.1 part by weight to perform a prepolymerization reaction.

(A) 0.1 to 10 parts by weight of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.1 to 10 μm and (b) 70 to 90 parts by weight of an isocyanate are reacted first to prepare a polyurethane carbon nanotube composite (C) a polyether polyol having a hydroxyl group content of 150 to 250 mgKOH / g is adjusted to 0 to 30 parts by weight in accordance with the NCO content of the prepolymer and is heated at a temperature of 50 to 90 ° C. for 2 to 4 hours And then reacted to prepare a polyurethane prepolymer having a low viscosity, a fast curing rate, a high molecular weight and a low NCO%.

The present invention relates to a process for producing a microporous foam sheet which is easy to control the thickness of the sheet and the size of the micropores when the polyurethane prepolymer is used in the form of a thin sheet, and has excellent mechanical strength, shock absorbability and sealing ability In particular, the polyurethane prepolymer can produce a curing agent having a faster curing rate than when a polyol is simply mixed on a subject.

The method for producing a high-molecular-weight polyurethane prepolymer having a low NCO content and low molecular weight is carried out by using polymeric methylene diphenyl diisocyanate (Cosmonate LL) produced by KUMHO MITSUI CHEMICAL CO. A polyurethane prepolymer curing agent can be produced.

(E) 10 to 20 parts by weight of a polycaprolactone polyol having a hydroxyl group content of 93 to 560 mg KOH / g, (f) 45 to 70 parts by weight of a polypropylene glycol having a hydroxyl group content of 28 to 56 mg KOH / g, (g) 0 to 30 parts by weight of a flame retardant, (i) 0.5 to 1.5 parts by weight of a nickel catalyst, (j) 5 to 29 parts by weight of a polyfunctional group polyol having a hydroxyl group content of 320 to 448 mgKOH / g, 3.0 parts by weight.

(E) having a molecular weight in the range of 200 to 1,200 and polypropylene glycol (f) having a molecular weight in the range of 2,000 to 4,000 can be used as the main component of the subject matter, and the polyfunctional group polyol (g) For example, a polyurethane resin (Mw = 300) at the OH end of the functional group trivalent is used by using trimethylpropane, and the flame retardant (h) is preferably a phosphorus flame retardant.

As the catalyst (i) applied to the subject, a catalyst selected from the group consisting of 1,8-diazacyclo (5,4,0) undec-7-ene or a nickel salt can be used. As the foam stabilizer (j), an anionic surfactant such as a silicone surfactant having a polydimethylsiloxane and a polyoxyalkylene chain, a fatty acid salt, a sulfuric acid ester salt, a phosphate ester salt, and a sulfonic acid salt may be used. The viscosity of the subject remains in the range of 400 to 600 cps / 25 ° C.

In producing the polyurethane foam sheet in the present invention, granular or layer-like fillers such as calcium carbonate, barium sulfate, silica, clay, talc, mica, and wollastonite may be used as fillers. Titanium dioxide, Carbon black, and the like. In addition to these, resins such as antioxidants, heat stabilizers, UV stabilizers, and additives for improving the stability of the urethane sheet can also be used.

In order to prepare a polyurethane foam sheet having homogeneous micropores, it is preferable that the polyurethane prepolymer curing agent to which the surface-treated carbon nanotubes are applied is blended in a ratio of NCO / OH molar ratio of 0.8 to 1.2, , The strength of the thin film is increased but the flexibility is poor and the physical properties such as 50% compressive load are increased. On the contrary, when the ratio is lowered, the formation ability of the pores and the strength of the sheet are lowered. The viscosity of the polyurethane resin composition immediately after the blending of the present invention is suitably adjusted in the range of 500 to 2,000 cps / 25 ° C. When the viscosity is too high, the flowability of the polyurethane resin is lowered and the uniform bubble and film can be formed There is no disadvantage.

The polyurethane resin blend resin is a polyurethane resin composition for a microporous foam sheet having a solids content of 100% by weight and does not contain an organic solvent. The polyurethane resin composition has a thickness of 70 to 120 탆, a density of 0.3 to 0.6 g / A foam sheet having a thickness of 10 to 30 탆 and a sheet strength of 4.5 to 7.2 kgf / cm 2 can be produced. The foam sheet is composed of a microporous EMI shielding / grounding compound having a stability of 60% or more and an electromagnetic wave shielding rate of 65 dB or more, Thereby forming a gasket (Shielding / Grounding Gasket).

Accordingly, the present invention is characterized by a polyurethane resin composition capable of producing a microencapsulated foamed sheet having characteristics superior in mechanical strength, releasability and tear strength to those of conventional foam sheets in terms of the thickness of a thin film.

In the pore forming step of the present invention, a foaming material such as a cream is formed while stirring at high speed in a mix head at a predetermined ratio of a subject having at least two OH groups containing a curing agent to which a carbon nanotube is applied and a polyfunctional polyol, A polyethylene terephthalate film or a polyether film to prepare a microporous sheet in the form of a thin film. Cooling water or an inert gas can also be applied to the mix head to control the most important creaming time of the coating.

A process for producing a microporous foam sheet according to the present invention, that is, a polyurethane foam sheet using a thin-film polyfunctional polyol is as follows.

First, 0.1 to 10 parts by weight of the carbon nanotubes (a) and 70 to 90 parts by weight of the isocyanate (b) are reacted first to prepare a polyurethane carbon nanotube composite, and then (c) a polyether polyol is mixed with a prepolymer And the mixture is reacted at a temperature of 50 to 80 ° C for 2 to 4 hours to prepare a polyurethane prepolymer curing agent having an NCO content of 10 to 20% by weight.

(E), polypropylene glycol (f), polyfunctional group polyol (g), flame retardant (h), catalyst (i), and stabilizer (j) are added to a reaction tank capable of high- ) And pigments and the like are mixed at a predetermined ratio to prepare a polyolefin mixed solution for 1 to 6 hours. The prepared prepolymer curing agent and an inert gas are then injected and stirred at a high speed to form a microporous urethane foam.

At this time, it is advantageous to keep the temperature of the mixed solution at 20 to 45 ° C, and the mixing agitation speed is set to 4,000 to 8,000 to form a uniform micropores by appropriately mixing the hardener and the non-reactive gas (inert gas) rpm, more preferably 5,000 to 7,000 rpm for about 1 to 2 minutes until a cream phase is obtained. A polyurethane resin composition for a urethane foam sheet can be prepared by using a mortar with a mesh size of 50 mesh or more in order to remove relatively large bubbles in the bubble dispersion at the time of discharging the dispersion. The obtained urethane foam is then subjected to heat treatment at a temperature of 100 to 150 ° C, preferably 120 to 140 ° C to accelerate the reaction, and the resulting thin sheet improves the tensile strength, tear strength and compressive strength characteristics.

In other words, the microcrystalline foam sheet of the present invention is prepared by mixing a hardener and a base in the presence of an inert gas and stirring at a high speed for about 1 to 2 minutes to form a creamy low-density polyurethane foam having uniform micropores, When a film is prepared by casting on a release paper such as a terephthalate film to a thickness of 70 to 120 μm and cured at a temperature of 100 to 150 ° C., a uniform density of 0.3 to 0.6 g / cm 3 and an average size of pores of 10 to 30 μm It is possible to produce a polyurethane foam sheet having micropores.

Further, the surface of the foam sheet is buffered here to prepare a polyurethane foam sheet from which the upper second layer or the lower second layer has been removed, the polyurethane foam sheet with the surface buried is vertically punched, and the perforated poly The composite material for EMI can be manufactured through the electroplating through the plating of the urethane foam sheet. At least one surface of the buffered polymer foam sheet may be punched after the conductive layer is formed. The conductive layer may be formed of a conductive mesh, a conductive nonwoven fabric, a conductive woven fabric, a conductive film, a metal film or a foil And is not necessarily limited thereto.

A conductive adhesive, a conductive hot melt, a conductive adhesive, and the like may be applied to at least one side of the plated polymer foam sheet, but the present invention is not limited thereto. When the conductive layer is assembled as described above, the mechanical strength such as the tensile strength of the conductive gasket is increased.

Next, a polyurethane resin composition for a thin film foam sheet using the polyfunctional group polyol according to the present invention will be described as an example. Hereinafter, a preferred embodiment The present invention will be described.

Surface treatment of carbon nanotubes

Surface treatment of carbon nanotubes to give functional groups such as -COOH and -OH on the surfaces of carbon nanotubes is carried out by mixing 5 g of carbon nanotubes (CNT) with 100 g of 30 mol% nitric acid (NH ₃ ) , The surface of the carbon nanotubes is activated by stirring for 2 to 24 hours, and then the surface-treated carbon nanotubes are treated with distilled water and acetone or methyl ethyl ketone using a filter apparatus. The mixture is filtered through a filter, and after confirming the pH, it is judged whether or not it is cleaned. The carbon nanotube powder is then dried in a dryer at a temperature of about 100 ° C for 24 hours. At this time, whether or not the formation of -COOH and -OH is confirmed through the peak of IR, and the hydroxyl group value is adjusted to 112 to 1,200 mgKOH / g to prepare isocyanatized carbon nanotubes in the next step.

Polyurethane Prepolymer  Curing agent preparation

30 g of the dried carbon nanotubes were mixed with 800 g of diphenylmethane diisocyanate (NCO% = 31.5%, DOW chemical) and a bismuth catalyst (K-KAT348, king industry) corresponding to 50 ppm of polyurethane resin At room temperature for 4 hours to prepare an isocyanatized carbon nanotube urethane composite, and the NCO content was measured. The reaction was continued until there was no change in the NCO content. Then, 100 to 170 g of polypropylene glycol was added thereto, and the reaction was continued until the NCO content reached 16% by weight or less to prepare a polyurethane prepolymer curing agent.

Subject manufacturing

Polypropylene glycol, polycaprolactone, trimethylpropane, flame retardant 1,3 propanediol, a catalyst, and a foam stabilizer were added to a mixing vessel of a stainless steel-made 3 L capacity and uniformly stirred at a high speed for about 5 hours or more in a nitrogen atmosphere, Deg.] C. and further stirring was performed at 300 rpm or less to prepare a subject.

Polyurethane resin compositions and Micrograph Foam sheet  Produce

A high-speed mixing head equipped with a mixer capable of high-speed agitation of 4,000 rpm or more was supplied with a polyurethane prepolymer hardener, a subject and inert gas at a constant rate using a metering pump. The mixture was uniformly mixed for 1 minute and 30 seconds, and then the interval (0.8-0.03 mm) between the comma knife and the release paper used as the base material was adjusted on the polyethylene terephthalate film and cast to a certain thickness. And then cured at a temperature in the range of 120 to 140 ° C to prepare a thin polyurethane foam sheet.

[Example 1] - [Example 1], [Comparative Example]

Table 1 below shows the raw materials of the polyurethane prepolymer hardener used in each of the Examples and Comparative Examples and the blending ratio thereof in order to produce the polyurethane resin composition.

Ingredient (parts by weight) Example 1 Example 2 Example 3 Example 4 Comparative Example MDI 80 80 80 80 80 Carbon nanotube 3 5 One 3 - Polyether polyol 17 10 22 15 20 catalyst 0.1 0.1 0.1 0.1 0.1

Table 2 shows the viscosity and NCO content of the polyurethane prepolymer curing agent prepared through each of the Examples and Comparative Examples.

division Example 1 Example 2 Example 3 Example 4 Comparative Example Viscosity (cps / 25 캜) 600 900 500 1000 400 NCO% 15 15 15 20 28

Table 3 shows the viscosities of the main raw materials reacted with the polyurethane prepolymer curing agent applied to each of the examples and the comparative examples and the resin according to the compounding ratio (parts by weight) thereof.

Raw material name Example 1 Example 2 Example 3 Example 4 Comparative Example PPG 70 70 70 70 70 PCL 15 15 15 15 15 TMP 15 15 15 5 0 Flame retardant 30 30 30 30 30 Foaming agent One One One One One catalyst One One One One One Foaming gas 10 10 10 10 10 Viscosity (cps / 25 캜) 500 500 500 400 300

[Experimental Example]

Table 4 shows the curing rate and the average pore size, tensile strength, 50% compressive load, permanent compression loss rate, and conductivity of the microporous foam sheet obtained by the reaction between the polyurethane prepolymer curing agent and the base material applied to each of the examples and the comparative examples The results are shown in Fig.

division Example 1 Example 2 Example 3 Example 4 Comparative Example Viscosity immediately after blending
(cps / 25 < 0 > C) 500 700 900 1,000 1,500 Hardening speed
(min) One One One 0.5 2 Average size of pores
(탆) 20 29 20 19 34 The tensile strength
(kgf / cm2) 6.01 7.2 4.9 6.2 4.1 50% compression load
(kg / cm2) 0.5 0.7 0.5 0.4 0.2 Permanent compression loss ratio
(%) 1.3 1.2 1.4 2 2.5 Thin sheet composite
Vertical resistance (Ω) 0.07 0.06 0.09 0.07 0.12

As shown in the results of Table 4, the microporous foam sheet made of the polyurethane resin composition of the present invention had uniform pore size and uniformity as compared with the comparative example in which the non-prepolymerized polyol was applied, It can be confirmed that it is very suitable for sheet of EMI gasket material because it is excellent in compression load and permanent compression loss ratio as well as excellent in conductivity and is effective in electromagnetic wave shielding.

Accordingly, the polyurethane resin composition for a microporous foam sheet manufactured according to the present invention can be variously substituted, modified and changed without departing from the technical idea of the present invention. It can be used for various applications and forms as functional material for adjacent technology which requires sealing function, insulation function and sound absorption function as well as gasket material for shock absorption and sealing property.

Claims (8)

(a) 0.1 to 10 parts by weight of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.1 to 10 탆, (b) 70 to 90 parts by weight of an isocyanate, (c) 0 to 30 parts by weight of an ether polyol (polyether polyol), and 0.1 part by weight of a bismuth carboxylate catalyst; (d) a polyurethane prepolymer curing agent; And
(e) 10 to 20 parts by weight of a polycaprolactone polyol having a hydroxyl group content of 93 to 560 mg KOH / g, (f) 45 to 70 parts by weight of a polypropylene glycol having a hydroxyl group content of 28 to 56 mg KOH / g, (g) (I) 0.5 to 1.5 parts by weight of a nickel catalyst, and (j) 0.5 to 3.0 parts by weight of a foam stabilizer; (c) 5 to 29 parts by weight of a polyfunctional polyol having a hydroxyl value of 448 mgKOH / g; The subject;
And a polyurethane resin composition for a microcellular foam sheet for an EMI gasket material.
The method according to claim 1,
Wherein the carbon nanotube (a) used in the polyurethane prepolymer curing agent is surface-treated with nitric acid (NHO ₃ ) to adjust the hydroxyl value to 112 to 1,200 mgKOH / g. Urethane resin composition.
3. The method of claim 2,
Wherein the surface-treated carbon nanotube is produced as a prepolymer of isocyanatized carbon nanotubes by reacting with the isocyanate (b).
The method of claim 3,
Wherein the isocyanatized carbon nanotubes are prepared in a molar ratio of 1: 2 to 1: 4 of the OH group of the carbon nanotubes having the hydroxyl value of the prepolymer and the NCO group of the diisocyanate. A polyurethane resin composition for a foam sheet.
The method of claim 3,
Wherein the polyol to be polymerized with the prepolymer of the isocyanatized carbon nanotubes is a polyfunctional polyol (g). The polyurethane resin composition for a microporous foam sheet for an EMI gasket material according to claim 1,
The method according to claim 1,
Wherein the polyurethane prepolymer curing agent has an NCO content of 10 to 20% by weight and a viscosity of 400 to 1,500 cps / 25 캜.
The method according to claim 1,
The polyurethane prepolymer curing agent and the base were mixed in a ratio of NCO / OH molar ratio of 0.8 to 1.2 to have a viscosity of 500 to 2,000 cps / 25 ° C, and an organic solvent-free solid content of 100 wt% Polyurethane resin composition for microcellular foam sheet for EMI gasket material.
A polyurethane resin composition according to any one of claims 1 to 7 having a thickness of 70 to 120 탆, a density of 0.3 to 0.6 g / cm 3, an average pore size of 10 to 30 탆, a sheet strength of 4.5 to 7.2 kgf / cm 2 Wherein the microporous foam sheet for EMI gasket material is formed of a thin film that is thinner than the microporous foam sheet.