KR101999516B1 - Conductive water-dispersible polyurethane resin composition for surface coating of emi gasket material and its manufacturing process - Google Patents

Abstract

The present invention relates to a conductive water dispersible polyurethane resin composition for surface coating of an EMI gasket material and a method of manufacturing the same. The conductive water dispersible polyurethane resin composition for surface coating of an EMI gasket material according to the present invention comprises: (a) 0.05 to 3% by weight of carbon nanotubes having an average length of 0.05 to 5 탆; (b) from 20 to 50% by weight of a diisocyante; (c) 7 to 49% by weight of polytetramethylene glycol; (d) 3 to 21% by weight of a polycarbonate diol; (e) 1 to 7% by weight of a reactive silicone compound; (f) 1 to 5% by weight of 2,2-bis (hydroxymethyl) butyric acid (DMBA); (g) 1 to 5 wt% of a neutralizing agent; (h) 2-8 wt% of a chain extender; (i) 5 to 10% by weight of a conductive polymer resin.
The method for producing a conductive water dispersible polyurethane resin composition for surface coating of an EMI gasket material comprises the steps of: (i) surface-modifying a carbon nanotube (a) having an average diameter of 1 to 50 nm and an average length of 0.05 to 5 탆, 112 to 500 mg KOH / g; (Ii) reacting the carbon nanotube (a) having the hydroxyl value with a diisocyanate (b) to prepare an isocyanatized carbon nanotube composite; (Iii) mixing the isocyanatized carbon nanotube composite with a polyether polyol mixed with polytetramethylene glycol (c) and polycarbonate diol (d), and a reactive silicone compound (e), 2,2-bis (F) to produce a polyurethane prepolymer; (Iv) a step of dispersing the prepared polyurethane prepolymer in water in which the neutralizing agent (g) is dispersed and reacting with the chain extender (h), followed by mixing the conductive polymer resin (i).
The conductive water dispersible polyurethane resin composition for surface coating of the EMI gasket material of the present invention is excellent in dispersibility in water by using an isocyanated carbon nanotube composite in which surface modified carbon nanotubes are isocyanated, Even when coated on the surface of the thin film foam sheet, the surface properties are excellent, such as tackiness, restitution, and traces of fingerprints during processing, and good abrasion resistance can be imparted.
In addition, the conductive water dispersible polyurethane resin composition for surface coating of the EMI gasket material produced by the production method of the present invention is prepared by preparing an isocyanatized carbon nanotube composite in the prepolymer stage, and then mixing the polyether polyol with the reactive silicone compound and the conductive polymer Since the effect of increasing the conductivity of the EMI gasket can be obtained through the application of the resin, it can be applied to a polyurethane thin film sheet having a thickness of 0.13t (130 μm) or less, so that the thin film sheet composite (3 * 3 mm) It is possible to manufacture a composite sheet for an EMI shielding / grounding gasket having a resistance of 0.4 Ω or less.

Description

TECHNICAL FIELD [0001] The present invention relates to a conductive water-dispersible polyurethane resin composition for surface coating of an EMI gasket material and a method for producing the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a conductive water dispersible polyurethane resin composition for surface coating of an EMI gasket material and a method of manufacturing the same. More particularly, the present invention relates to a conductive polyurethane resin composition for surface coating, To a conductive water dispersible polyurethane resin composition for use in the surface treatment of thin film foam sheets used for absorption, sealing, and electromagnetic shielding, and a method for producing the same.

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 for parts for wearable and Internet (IoT) devices as well as smartphones.

It is required to elaborate various components and to minimize the size thereof in accordance with the tendency of miniaturization and thinning of electronic devices. Also, the gasket for sealing between internal parts and the case is required to have a minimum thickness and at the same time, The development of a material having a high thermal conductivity is required. In order to cope with such products having various materials and gaps, it is necessary to realize excellent impact absorbability, compressibility and conductivity even 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, researches on the thinning of gaskets due to the miniaturization of electronic devices have been actively conducted. Also, in the field of urethane materials development, various polyols have been developed, but a two-component polyurethane In the case of the foam sheet, it is known that the cushioning retention due to use for a long time is weakened, the thickness deviation is large, and the thinning is difficult.

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 is increased more than a certain amount, the reaction rate is slowed, and tensile strength, elongation and elastic modulus are lowered. In order to develop microcracked foam sheet for high resilience EMI gasket material, It is essential to improve flowability, workability, mechanical properties, elasticity and permanent compression reduction.

Particularly, as the foam sheet becomes thinner, the sticky tackiness of the surface increases, and there is a high possibility that defects such as fingerprints remain on the surface during processing, and the surface properties using the urethane resin can improve the surface properties , Water-dispersible polyurethane resins are mainly used due to the problems of harmfulness and odor of VOCs during operation due to the use of oil-based and aqueous polyurethane resins.

However, when using a general water-dispersible polyurethane resin, tacky may be generated on the surface, the fingerprint prevention and contamination resistance may be low, and the conductive property when used as an EMI grounding / shielding gasket The phenomenon of deterioration is confirmed.

In addition, various methods are used to impart conductivity in a polymeric material. In the case of a water-dispersible polyurethane resin, however, in comparison with resins prepared in a solvent or bulk form, When a positive conductive material is applied and the conductivity is increased, the dispersibility is deteriorated so that phase separation or easy precipitation is observed.

The thinner the sheet is, the less the strength of the sheet itself tends to decrease and the processability tends to deteriorate. This can be improved by controlling the content of the polyol or treating the reinforcing agent, and application of carbon nanotubes is also known as an effective method for improving the strength and conductivity of the sheet.

Conventional carbon nanotubes are entangled because they are aggregated into bundles by a strong van der waals force. If carbon nanotubes are in such a state in a matrix, they can exhibit their inherent properties It is impossible to substantially provide conductivity and the mechanical properties may be deteriorated. 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. In the present invention, a functional group such as -COOH or -OH is formed on the surface of a carbon nanotube by acid treatment to increase dispersibility and strength in a urethane matrix, and the carbon nanotube composite is first reacted with isocyanate to form a carbon nanotube composite To prepare a polyurethane prepolymer.

In the prior art related to the polyurethane foam used as a gasket material according to the present invention, Korean Patent Laid-Open Publication No. 10-2006-0131433 (Applicant: Decanix) discloses a metal thin film layer and a metal thin film layer, A conductive polymer resin coating layer coated with a polymer resin coating agent; a film layer laminated on the other side of the metal thin film layer; a fabric layer laminated on the other side of the film; and a hot melt layer formed on the other side of the fabric layer, The sponge is wrapped with the sponge, and at the same time, the sponge is bonded to the sponge while being fused by the heat generated from the gasket manufacturing apparatus, thereby forming a gasket, thereby preventing the electromagnetic wave from leaking out from the outside or penetrating from the outside to the inside in various seams, Or as a grounding wire for electronic circuits, which may cause circuit damage due to electrostatic discharge (ESD). A block, using the thin metal film coating the fabric surface with an electrically conductive polymer resin that can prevent discloses an electromagnetic wave shielding gasket sponge.

In addition, as disclosed in Japanese Patent Application Laid-Open No. 10-2006-0135200 (Applicant: SENKE POLYTE TECH CO., LTD.), Spacer gasket for shielding electromagnetic interference (EMI) / radiofrequency interference (RFI) sheet and a method for producing the same. According to the present invention, a polymeric elastomer sheet is laminated on one side of a base film, a conductive material layer is laminated on the other side of the base film, A sheet for a spacer gasket produced by forming a plurality of cut-out portions that are cut through a body sheet and coating an upper elastic sheet surface of the sheet of the laminate and an inner wall of a cut surface of the cut portion with a conductive paint layer, Of high impact resistance, vibration barrier properties and strength, while maintaining high-level surface conductivity and vertical conductivity at the same time It is very useful for EMI and RFI shielding gasket manufacturing of electronic communication equipments by simultaneously maximizing shock absorption and vibration shielding, EMI / RFI shielding and excellent sealing.

Also, a method for producing a conductive polyurethane resin composite in which carbon nanotubes are uniformly dispersed in the above-mentioned Patent Registration No. 10-1182723 (Applicant: Korean Footwear Research Institute, etc.) is a method of mixing a carbon nanotube and a polyol to prepare a mixture And dispersing the carbon nanotubes in the polyol, wherein the dispersing step comprises a step of subjecting the mixture to a ball mill treatment, a step of treating the mixture by ultrasonic treatment And the step of treating the mixture with a roll mill, wherein the carbon nanotubes are not chemically pretreated to form a functional group other than carbon, and the polyol composition comprises the carbon nanotube And that the carbon nanotubes are not uniformly dispersed in the carbon nanotubes have.

The conductive composition having excellent electrical conductivity and dispersibility disclosed in the above-mentioned Patent Registration No. 10-1759833 (Applicant: Yonsei University, Industry & Academy Collaboration) and a method for producing the same are useful for controlling the acidity of a solution containing a conductive polymer resin and an ionic polymer electrolyte. The dispersibility of the polyurethane can be improved and the aggregation of the polyurethane particles can be prevented to improve the uniformity of the conductive polymer resin solution and the low haze And the cured coating film prepared by curing the conductive composition may have excellent electrical conductivity and antistatic property.

Meanwhile, in the present invention, the surface-treated carbon nanotube composite is reacted with a diisocyanate to prepolymerize, and the polyether polyol is chemically bonded to the reactive silicone compound and the conductive polymer resin in the aqueous polyurethane prepolymer chain, A conductive polyurethane resin composition for surface coating of an EMI gasket material having improved characteristics, stability and conductivity has been developed and the present invention has been completed.

Korean Patent Publication No. 10-2006-0131433 (published on December 20, 2006) Korean Patent Publication No. 10-2006-0135200 (published on December 29, 2006) Korean Patent Registration No. 10-1182723 (Published on Mar. 13, 2012) Korean Registered Patent No. 10-1759833 (Published on July 27, 2017)

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a water-dispersible polyurethane resin for surface treatment of an EMI shielding / grounding gasket material, which comprises forming a small amount of an isocyanatized carbon nanotube composite in a prepolymer stage, Dispersible polyurethane resin composition for surface coating of an EMI gasket material having excellent dispersibility, surface characteristics, good abrasion resistance and resilience by applying a reactive silicone compound, a conductive polymer resin, and the like, and a method for manufacturing the same.

(A) 0.05 to 3% by weight of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.05 to 5 占 퐉; (b) from 20 to 50% by weight of a diisocyante; (c) 7 to 49% by weight of polytetramethylene glycol; (d) 3 to 21% by weight of a polycarbonate diol; (e) 1 to 7% by weight of a reactive silicone compound; (f) 1 to 5% by weight of 2,2-bis (hydroxymethyl) butyric acid (DMBA); (g) 1 to 5 wt% of a neutralizing agent; (h) 2-8 wt% of a chain extender; (i) 5 to 10% by weight of a conductive polymer resin.

According to a preferred embodiment of the present invention, the carbon nanotube (a) is modified to have a hydroxyl value of from 112 to 500 mgKOH / g and the diisocyanate (b) is 4,4'-methylene Dicyclohexyl diisocyanate (H ₁₂ MDI) and isophorone diisocyanate are mixed in a weight ratio of 5 to 7: 3 to 5, and the reactive silicone compound (e) is polydimethyl siloxane , And the conductive polymer resin (i) is an aqueous solution of polyethylene dioxythiophene / polystyrene sulfonate (PEDOT / PSS) dispersion.

In addition to the above polyurethane resin composition, 0 to 5 wt% of precipitated silica and polydimethylsilicon dispersion having a particle size of 1 to 10 mm, which are not surface-treated, are added to the total weight of the resin composition It is possible.

Accordingly, the polyurethane resin composition has a viscosity of 100 to 1,500 cps / 25 占 폚, an organic solvent-free, and a solid content of 25 to 35% by weight.

The method for producing a conductive water dispersible polyurethane resin composition for surface coating of an EMI gasket material comprises the steps of: (i) surface-modifying a carbon nanotube (a) having an average diameter of 1 to 50 nm and an average length of 0.05 to 5 탆, 112 to 500 mg KOH / g; (Ii) reacting the carbon nanotube (a) having the hydroxyl value with a diisocyanate (b) to prepare an isocyanatized carbon nanotube composite; (Iii) mixing the isocyanatized carbon nanotube composite with a polyether polyol mixed with polytetramethylene glycol (c) and polycarbonate diol (d), and a reactive silicone compound (e), 2,2-bis (F) to produce a polyurethane prepolymer; (Iv) dispersing the prepared polyurethane prepolymer in water in which the neutralizing agent (g) is dispersed, reacting the resultant polyurethane prepolymer with the chain extender (h), and then mixing the conductive polymer resin (i) Wherein the molar ratio of the OH group of the carbon nanotube to the NCO group of the diisocyanate is 1: 5 to 8.

The conductive water dispersible polyurethane resin composition for surface coating of the EMI gasket material of the present invention is excellent in dispersibility in water by using an isocyanated carbon nanotube composite in which surface modified carbon nanotubes are isocyanated, Even when coated on the surface of the thin film foam sheet, the surface properties are excellent, such as tackiness, restitution, and traces of fingerprints during processing, and good abrasion resistance can be imparted.

In addition, the conductive water dispersible polyurethane resin composition for surface coating of the EMI gasket material produced by the production method of the present invention is prepared by preparing an isocyanatized carbon nanotube composite in the prepolymer stage, and then mixing the polyether polyol with the reactive silicone compound and the conductive polymer Since the effect of increasing the conductivity of the EMI gasket can be obtained through the application of the resin, it can be applied to a polyurethane thin film sheet having a thickness of 0.13t (130 μm) or less, so that the thin film sheet composite (3 * 3 mm) It is possible to manufacture a composite sheet for an EMI shielding / grounding gasket having a resistance of 0.4 Ω or less.

Hereinafter, the conductive water dispersible polyurethane resin composition for surface coating of the EMI gasket material according to the present invention and a method of manufacturing the same will be described. However, the present invention is not limited thereto. The present invention is not intended to limit the technical spirit and scope of the present invention.

The polyurethane resin composition according to the present invention comprises (a) 0.05 to 3 wt% of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.05 to 5 탆, the surface of which is modified to have a hydroxyl value of 112 to 500 mgKOH / %; (b) 20 to 50 diisocyantes obtained by mixing 4,4'-methylenedicyclohexyl diisocyanate (H ₁₂ MDI) and isophorone diisocyanate in a weight ratio of 5 to 7: 3 to 5; weight%; (c) 7 to 49% by weight of polytetramethylene glycol; (d) 3 to 21% by weight of a polycarbonate diol; (e) 1 to 7% by weight of a reactive silicone compound made of polydimethylsiloxane; (f) 1 to 5% by weight of 2,2-bis (hydroxymethyl) butyric acid (DMBA); (g) 1 to 5 wt% of a neutralizing agent; (h) 2-8 wt% of a chain extender; (i) 5 to 10% by weight of a conductive polymer resin comprising an aqueous dispersion of polyethylene dioxythiophene / polystyrene sulfonate (PEDOT / PSS), wherein the polyurethane resin composition comprises (i) (A) having an average length of 0.05 to 5 탆, and adjusting the hydroxyl value to 112 to 500 mgKOH / g; (Ii) reacting the carbon nanotube (a) having the hydroxyl value with a diisocyanate (b) to prepare an isocyanatized carbon nanotube composite; (Iii) mixing the isocyanatized carbon nanotube composite with a polyether polyol mixed with polytetramethylene glycol (c) and polycarbonate diol (d), and a reactive silicone compound (e), 2,2-bis (F) to produce a polyurethane prepolymer; (Iv) a step of dispersing the prepared polyurethane prepolymer in water in which the neutralizing agent (g) is dispersed, reacting the resultant with the chain extender (h), and then mixing the conductive polymer resin (i).

First, in step (i), a single-walled carbon nanotube (a) having an average diameter of 1 to 50 nm and an average length of 0.05 to 5 占 퐉 and a purity of 95 wt% or more is prepared to prepare an isocyanatized carbon nanotube composite. When the carbon nanotube (a) has an average diameter of less than 1 nm and an average length of less than 0.05 탆, the size of the nanotubes is excessively small, so that the viscosity of the resin during formation of the prepolymer or after the blending is too high, It is not sufficient to exhibit sufficient physical properties, and even when the average diameter is 50 nm and the average length exceeds 5 占 퐉, the dispersibility becomes poor.

The amount of the carbon nanotubes (a) is preferably in the range of 0.05 to 3% by weight based on the total weight of the resin composition. When the amount of the carbon nanotubes is too small, the electrical conductivity is significantly deteriorated. There is a possibility that phase separation occurs due to the poor dispersibility in the dispersion.

As an example of the step of surface-modifying the carbon nanotube (a) in order to impart functional groups such as -COOH and -OH to the surface of the carbon nanotube (a), 100 g of a 30 mol% nitric acid solution (NHO ₃ ) And 3 g of nanotubes. The mixture was stirred at 70 to 90 ° C. for 2 to 24 hours to activate the surface of the carbon nanotubes, and the surface-modified carbon nanotubes (a) were mixed with distilled water and acetone or methyl ethyl ketone (Methyl ethyl ketone), and the resultant is filtered for five times. After confirming the pH, the carbon nanotube powder is prepared by drying in a dryer at 100 ° C. for 24 hours. At this time, by confirming the formation of -COOH and -OH through the peak of IR, the hydroxyl group value can be adjusted to 112 to 500 mgKOH / g to effectively prepare an isocyanatized carbon nanotube complex in the next step.

In order to perform the surface modification process of the carbon nanotube (a), the carbon nanotube powder can be treated using a refluxing nitric acid solution.

In order to obtain a stable polyurethane resin having a uniform molecular weight as described above, the hydroxyl value of the carbon nanotube (a) to be reacted with isocyanate should be controlled in the range of 112 to 500 mgKOH / g, (A) has a small number of functional groups on the surface of the carbon nanotube (a), the reactivity with the isocyanate is poor. When it exceeds 500 mgKOH / g, a large number of isocyanates are bonded to the surface of the carbon nanotube Phase separation occurs when dispersed.

In the present invention, the hydroxyl value of the surface of the washed and dried carbon nanotube (a) is measured. When the hydroxyl value is insufficient, the concentration of nitric acid (NH ₃ ), the reaction temperature, (A), which is activated only at a portion of the hydrophilic surface that has been adjusted to have a hydrophilic surface.

Next, in the step (ii), the surface-treated carbon nanotube (a) is reacted with a diisocyanate (b) to prepare an isocyanatized carbon nanotube composite. In the above process, the -OH and -COOH groups of the carbon nanotubes (a) whose surface hydroxyl groups have been controlled are subjected to urea and urethane reaction with a liquid type diisocyanate to form an isocyanatized carbon nanotube composite-urethane monomer and / ≪ / RTI >

The method for producing an isocyanate-modified carbon nanotube composite by reacting the carbon nanotube (a) having a controlled hydroxyl value and the diisocyanate (b) is not particularly limited, and the diisocyanate (b) Can be obtained by stirring in the presence of the tube (a) and a known catalyst for preparing urethane, or at a temperature of 90 to 110 캜 for 3 to 24 hours while adding an inhibitor. The molar ratio of the NCO group of the OH group: diisocyanate (b) of the carbon nanotube (a) whose hydroxyl value is adjusted in the step of producing the isocyanatized carbon nanotube composite is adjusted to 1: 2 to 10. Preferably, a ratio of 1: 5 to 8 is most suitable, and a bismuth carboxylate catalyst may be added to accelerate the complexation reaction.

The diisocyanate (b) used in the present invention is preferably 4,4'-methylenedicyclohexyl diisocyanate (H ₁₂ MDI), isophorone diisocyanate, tetramethyl xylene diisocyanate, hexamethylene Diisocyanate (hexamethylene diisocyanate) may be used. However, considering the stability of the reaction and the flexibility required for the EMI shielding / grounding gasket, the diisocyanate (b) It is preferable to use a mixture of methylene dicyclohexyl diisocyanate (H ₁₂ MDI) and isophorone diisocyanate in a weight ratio of 5 to 7: 3 to 5, and diisocyanate (b) (OH / NCO ratio) of 1.0 to 1.9, more preferably 1.0 to 1.5, in terms of equivalent ratio It is most preferable to use a regulated 20 to 50% by weight.

In the step (iii) of producing the polyurethane prepolymer in the present invention, the carbon nanotube composite obtained by isocyanating by the step (ii) is preferably a mixture of polytetramethylene glycol (c) and polycarbonate diol (B), a polyether polyol, and a reactive silicone compound (e) and 2,2-bis (hydroxymethyl) butyric acid (f), followed by a step of raising the temperature to 90 ° C and a step of adding a bismuth carboxylate catalyst Followed by cooling down to 60 ° C.

As the polyether polyol, it is possible to use polytetramethylene glycol (PTMG), polycarbonate diol, polypropylene glycol and at least one polyether polyol derived therefrom (PTMG) (c) having a weight-average molecular weight of 1,000 to 2,000 and a polycarbonate diol (d) are mixed with each other to obtain the strength and flexibility required for the aqueous dispersion type polyurethane resin coating layer It is possible to exercise.

Also, the reactive silicone compound (e) can be prepared by applying a polydimethylsiloxane having -OH groups at both terminals in a range of 1 to 7 wt% based on the total weight of the resin composition, so that interaction between the hydrophilic chains at the surface of the particles The dispersibility and stability can be improved and the viscosity can be lowered. As the reactive silicone compound (e), it is preferable to use a diterminal dicarbinol dimethyl polysiloxane having a molecular weight in the range of 600 to 2,000. Through this, it is possible to improve the flowability of the resin, A coating layer having characteristics can be formed.

In the present invention, polycarbonate diol (d) and diterminal dicarbinol dimetyl polysiloxane polyol (e) are added to improve the tacky and contamination characteristics of the surface of the coated material. It was found that it is most preferable to use the two at the same time.

DMBA (f) is contained in an amount of 1 to 5% by weight based on the total weight of the resin composition. DMBA used as an ionizing agent is a compound having flexibility of water-dispersed polyurethane It is possible to reduce the amount of the ion-introducing agent that causes the deterioration to a minimum and to react while preventing the deterioration of the dispersion stability, which is a disadvantage of the ionic prepolymer, thereby making it possible to produce a highly efficient water-dispersed polyurethane resin.

In the final step (iv), the polyurethane prepolymer prepared as described above is dispersed in water in which the neutralizing agent (g) is dispersed and reacted with the chain extender (h), followed by mixing the conductive polymer resin (i) Thereby producing a polyurethane resin.

In the above step, the polyurethane prepolymer prepared through the step (iii) is dispersed in water containing 1 to 5% by weight of a neutralizing agent (g) to prepare a prepolymer dispersion, and then a chain extender (h) (I) is mixed with 5 to 10% by weight of a conductive polymer resin, and the polyurethane prepolymer is mixed with deionized water maintained at 20 to 30 DEG C for 10 to 30 (H). When the temperature of the water is higher than 30 ° C, side reactions with the polyurethane prepolymer are caused and the physical properties are deteriorated.

The chain extender (h) may be selected from hydrazine, 1,3-bis (aminomethyl) cyclohexane, ethylene diamine and the like. The resin was found to have the most excellent physical properties.

Also, in the present invention, when a large amount of carbon nanotubes are used in a water-dispersible polyurethane resin, dispersibility is lowered, so that a large amount of an isocyanatized carbon nanotube composite can not be used and sufficient conductivity is difficult to develop. Resin (i) is applied.

The conductive polymer resin (i) may be polyethylenedioxythiophene / polystyrene sulfonate (PEDOT / PSS) or polyaniline / polystyrene sulfonate (PANI / PSS) having a molecular weight of 500 to 1000, It is more preferable to use a PEDOT / PSS dispersion aqueous solution prepared by mixing polyethylene dioxythiophene (PEDOT) having excellent electrical conductivity, chemical and thermal stability with polystyrene sulfonic acid (PSS). The amount of the conductive polymer resin (i) to be used is 5 to 10% by weight based on the total weight of the resin composition. Thus, the conductive polymer resin (i) is suitable for exhibiting its properties while maintaining the physical properties of the polyurethane resin. .

When the PEDOT / PSS dispersion aqueous solution is directly applied to the polyurethane prepolymer and then mixed, it becomes difficult to control the particles at the time of dispersion due to the low pH. Therefore, the chain extender (h) is added and the mixture is poured into the polyurethane resin desirable.

Bismuth carboxylate and the like used as other catalysts are well known in the field of the present invention, and detailed description thereof will be omitted.

The composite sheet for EMI shielding / grounding gasket may be impregnated with the polyurethane resin composition to prepare a surface coating. In addition, a hydrophilic quencher , A silicone dispersion, a thickener, a defoaming agent, and the like in an amount of 0 to 5% by weight, respectively, and coating the composite sheet with the polyurethane resin composition.

For example, a polyurethane resin composition prepared according to the present invention may be used to surface-coat a thickener or water according to the viscosity required to achieve the required viscosity, It is more preferable to additionally add a blend liquid prepared by mixing in a primary order to adjust the viscosity according to the extinction characteristics of the coating layer and the degree of surface slip property imparted thereto. As the quenching agent, silica obtained through pyrolysis or precipitation can be used, but a non-surface-treated precipitated silica having a particle size of 1 to 10 mm is preferable, and a silicone dispersion is prepared by dispersing a polydimethylsilicone dispersion in a poly It is possible to use them individually or in combination within 5% by weight based on the total weight of the urethane resin composition.

Accordingly, the conductive water-dispersible polyurethane resin composition for surface coating of the EMI gasket material of the present invention has a viscosity of 100 to 1,500 cps / 25 ° C, and does not contain any organic solvent but has a solid content of 25 to 35% by weight.

The water dispersible polyurethane resin developed through the present invention can be applied to a thin film urethane foam sheet to produce EMI shielding / grounding gasket products. At this time, the thin urethane foam sheet is buffed to form a polyurethane foam sheet from which the upper second layer or the lower second layer has been removed. The polyurethane foam sheet is then plated on the perforated polyurethane foam sheet to form a conductive material , And at least one surface of the buffered polymer foam sheet can be perforated after the step of fabricating the conductive layer.

The conductive layer may be a conductive mesh, a conductive nonwoven fabric, a conductive woven fabric, a conductive film, a metal film, or a foil, but is not limited thereto. After the impregnated polyurethane resin solution with the processed foam sheet was impregnated with the aqueous dispersion type polyurethane resin solution, a compression process using a mangle was carried out 2 to 5 times, and then a compression process was carried out at 60 ° C, 80 ° C, 100 ° C, 120 ° C and 150 ° C Each can be dried for 30 seconds to 5 minutes to produce an EMI gasket (Shielding / Grounding Gasket) material.

Hereinafter, an experimental example of a conductive water dispersible polyurethane resin composition for surface coating of an EMI gasket material according to the present invention will be described. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention will be described.

[Example 1]

Carbon nanotube surface modification

60 g of carbon nanotubes (CNT) were mixed with 2 kg of a 30 mol% nitric acid solution (NHO ₃ ) and agitated in a 3 L reactor at 70 to 90 ° C for 3 to 12 hours to activate the surfaces of the carbon nanotubes. Acetone or Methyl ethyl ketone was used to filter the solution five times. The pH of the solution was checked to determine whether it was cleaned, and the solution was dried in a dryer at 100 ° C for 24 hours to obtain a carbon nanotube powder And the formation of -COOH and -OH is confirmed through the peak of IR, and the hydroxyl value is adjusted to 112 to 500 mgKOH / g.

Manufacture of Carbon Nanotube Composites

Next, 30 g of the dried carbon nanotube powder was mixed with 204 g of a mixture of 4,4'-methylenedicyclohexyl diisocyanate (H ₁₂ MDI) and isophorone diisocyanate (IPDI) (weight ratio of 6: 4) (K-KAT348, king industry), which is a catalyst corresponding to 50 ppm, at 90 ° C for 4 hours to prepare an isocyanate-modified carbon nanotube composite, and the NCO% value was measured. Finally, the NCO% Was 8% or less, to prepare an isocyanatized carbon nanotube composite (NCO-CNT).

Preparation of polyurethane prepolymer

(Hydroxymethyl) propanoic acid (DMPA), 20 g of monoterminated modified silicone (FMDA11), 20 g of polytetramethylene glycol (PTMG1000), 120 g of polycarbonate polyol (T5650J) 31 g are uniformly mixed. 38.2 g of a carbon nanotube composite (NCO-CNT) was added thereto and stirred to uniformly mix at 90 ° C. After exothermic reaction, bismuthcarboxylate (K-KAT 348) catalyst was added and reacted at 110 ° C. for 3 hours And then cooled to 60 ° C.

Dispersion and chain extension

23 g of TEA was added to 2120 g of deionized water (23 DEG C) and stirred for 30 minutes. Thereafter, 867 g of a polyurethane prepolymer was added to the deionized water mixed solution within 30 minutes while maintaining the temperature of the water at 23 to 30 ° C to carry out dispersion. Then, 39 g of ethylenediamine was diluted with 210 g of deionized water and added to perform extension reaction, and then 71 g of PEDOT / PSS was added and mixed. As a result, an aqueous dispersion type polyurethane resin composition having a solid content of 30% and a viscosity of 800 cps / 25 캜 was obtained.

Manufacture of EMI gasket material

A resin solution containing a mixture of 3 g of a quencher and 1 g of a silicone dispersion was added to 100 g of the aqueous dispersion type polyurethane resin composition obtained through the above process, and then a resin solution was prepared by punching and surface-buffering the thin film urethane foam sheet And then the resin solution was impregnated with the plated foam sheet composite. Then, the resin sheet was subjected to a compression process using mangles 2 to 5 times and then subjected to a compression process at 60 ° C, 80 ° C, 100 ° C, 120 ° C and 150 ° C Each was dried for 30 seconds to 5 minutes to produce an EMI shielding / grounding gasket material.

[Comparative Example 1]

In Comparative Example 1, a polyurethane prepolymer was prepared in the same manner as in Example 1 except that isocyanatized carbon nanotubes were not used and dispersed and chain extended to obtain an aqueous dispersion type polyurethane resin composition. In Example 1 , A foam sheet was impregnated with a resin solution to prepare an EMI shielding / grounding gasket material.

[Comparative Example 2]

In Comparative Example 2, a polyurethane prepolymer was prepared in the same manner as in Example 1, except that the reactive silicone compound, that is, monotrimer denatured silicone (FMDA11) was not used, and dispersed and chain extended to prepare a water dispersible polyurethane resin composition And a foam sheet was impregnated into the resin solution prepared in the same manner as in Example 1 to prepare an EMI shielding / grounding gasket material.

[Comparative Example 3]

In Comparative Example 3, a polyurethane prepolymer was prepared in the same manner as in Example 1, except that dispersion and chain extension were performed in TEA-water without using a conductive polymer resin, and dispersed and chain extended to prepare an aqueous dispersion type polyurethane resin composition And a foam sheet was impregnated with the resin solution prepared in the same manner as in Example 1 to prepare an EMI shielding / grounding gasket material.

[Experimental Example 1]

The results of measurement of the physical properties of the aqueous dispersion type polyurethane resin compositions of Examples and Comparative Examples 1 to 3 are shown in Table 1 below.

division Example Comparative Example 1 Comparative Example 2 Comparative Example 3  Solid content (%) 30 29.7 29.6 28.5  Viscosity (cps / 25 캜) 800 500 600 700  pH 8.0 8.0 8.0 8.8  Thickness (㎛) 10 10 10 10  100% Mod. (Kgf / cm2) 22 17 25 28  Tensile strength (kgf / cm2) 210 190 230 250  Elongation (%) 400 500 350 400

※ The tensile strength and 100% modulus (modulus at 100% elongation) are measured by ASTM E252 method.

As shown in the above measurement results, in Comparative Example 1 in which isocyanatized carbon nanotubes were not applied, the tensile strength and 100% Mod. Were slightly lowered and the viscosity was greatly decreased. In the case of Comparative Example 2 in which the reactive silicone compound was not applied, the strength of the film was increased but the flexibility was lowered. In the case of Comparative Example 3 in which the conductive polymer resin was not applied, there was no significant change in elongation, and the strength of the film was increased but the pH was increased.

[Experimental Example 2]

The results of evaluating the physical properties of the EMI shielding / grounding gasket material of Examples and Comparative Examples 1 to 3 are shown in Table 2 below.

division Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3  Sticky (tacky) ◎ ◎ ◎  Surface contamination characteristics (fingerprint formation) ◎ ◎ ◎ Thin sheet composite (3 * 3 mm)
Vertical resistance (Ω) 0.4 0.6 0.4 0.8

※ Evaluation result: Excellent ◎>> X bad

As a result of comparing the coated materials as described above, it was confirmed that the comparative example 1 and the comparative example 3 in which the isocyanatized carbon nanotube or the conductive polymer resin was not applied tend to increase the vertical resistance of the thin film sheet composite, In the case of Comparative Example 2 in which no compound was applied, it was confirmed that the surface contamination characteristics and stickiness became a problem.

Accordingly, the conductive water dispersible polyurethane resin composition for surface coating of the EMI gasket material manufactured according to the present invention can be variously substituted, modified and changed within the scope of the technical idea of the present invention. It is a functional material that can be applied to materials requiring surface treatment and can be used in various applications and forms.

Claims (8)

(a) 0.05 to 3% by weight of carbon nanotubes having an average diameter of 1 to 50 nm and an average length of 0.05 to 5 탆, the surface of which is modified to have a hydroxyl value of 112 to 500 mgKOH / g;
(b) 20 to 50 diisocyantes obtained by mixing 4,4'-methylenedicyclohexyl diisocyanate (H ₁₂ MDI) and isophorone diisocyanate in a weight ratio of 5 to 7: 3 to 5; weight%;
(c) 7 to 49% by weight of polytetramethylene glycol;
(d) 3 to 21% by weight of a polycarbonate diol;
(e) 1 to 7% by weight of a reactive silicone compound made of polydimethylsiloxane;
(f) 1 to 5% by weight of 2,2-bis (hydroxymethyl) butyric acid (DMBA);
(g) 1 to 5 wt% of a neutralizing agent;
(h) 2-8 wt% of a chain extender;
(i) 5 to 10% by weight of a conductive polymer resin comprising an aqueous solution of polyethylene dioxythiophene / polystyrene sulfonate (PEDOT / PSS) dispersion;
Wherein the surface of the EMI gasket material is coated with a conductive polyurethane resin. delete delete delete The method according to claim 1,
In addition to the polyurethane resin composition, 0 to 5% by weight of precipitated silica and polydimethylsilicon dispersion having a particle size of 1 to 10 mm, which are not surface-treated, are added to the total weight of the resin composition A conductive water dispersible polyurethane resin composition for surface coating of an EMI gasket material. 6. The method according to any one of claims 1 to 5,
Wherein the polyurethane resin composition has a viscosity of 100 to 1,500 cps / 25 占 폚, does not contain an organic solvent, and has a solids content of 25 to 35% by weight. (I) a step of modifying the surface of the carbon nanotube (a) having an average diameter of 1 to 50 nm and an average length of 0.05 to 5 占 퐉 to adjust a hydroxyl value to 112 to 500 mgKOH / g;
(Ii) reacting the carbon nanotube (a) having the hydroxyl value with a diisocyanate (b) to prepare an isocyanatized carbon nanotube composite;
(Iii) mixing the isocyanatized carbon nanotube composite with a polyether polyol mixed with polytetramethylene glycol (c) and polycarbonate diol (d), and a reactive silicone compound (e), 2,2-bis (F) to produce a polyurethane prepolymer;
(Iv) dispersing the prepared polyurethane prepolymer in water in which the neutralizing agent (g) is dispersed, reacting the polyurethane prepolymer with the chain extender (h), and then mixing the conductive polymer resin (i);
Wherein the surface of the EMI gasket material is coated with a conductive polyurethane resin. 8. The method of claim 7,
The isocyanate-modified carbon nanotube composite of the step (ii) has a molar ratio of OH group: diisocyanate NCO group of the carbon nanotubes having a hydroxyl value adjusted to 1: 5 to 8. A method for producing a conductive polyurethane resin composition for water dispersion.