KR100266938B1 - Water-based thermosetting resin emulsions for electronic devices - Google Patents

Abstract

Removal of large amounts of organic solvents in the manufacture of printed wiring circuit boards may be possible using aqueous epoxy resin emulsions. The preparation of high quality in-spec prepregs from aqueous epoxy resin emulsions has been demonstrated in laboratory and laboratory scale processors. Prepregs are the same as those prepared by conventional organic solvent methods, which have the same level of B-state cure and comparable fluidity. Laminates made from prepregs have equivalent or improved temperature, adhesion and water absorption.

Description

Aqueous thermosetting resin emulsion for electronic device {WATER-BASED THERMOSETTING RESIN EMULSIONS FOR ELECTRONIC DEVICES}

The present invention relates to an aqueous thermosetting resin emulsion for producing electronic devices, packaging materials and printed circuit boards.

Printed circuit boards (PCBs) are composites composed of resins, generally epoxy resins, reinforcements, generally woven glass fabrics, and copper circuits. PCB is manufactured by impregnating a glass fabric into a laminated resin using a treatment tower. The impregnation method involves coating the woven glass fabric with a thermosetting resin solution to form a tacky stable material referred to as prepreg. The glass fabric acts as a reinforcement that controls the thermal expansion of the carrier and circuit boards on which the resin coating is deposited. The conventional method has two steps. The first step involves evaporating the organic solvent from the solution and the second step partially cures the resin to the desired state referred to as the B-state. Several sheets of prepreg are then inserted between the sheets of the surface treatment copper foil and laminated at elevated temperature and pressure to fully cure the resin-glass composite with a copper coated laminate. These laminates, often referred to as cores, are circuitd using photolithographic methods to form circuit boards. Multiple cores may be stacked together to form a multilayer circuit board using sheets or sheets of prepreg between cores.

Resin using large amounts of volatile organic compounds (VOCs), such as acetone, methyl ethyl ketone (MEK), toluene, methyl cellosolve (MCS), dimethylformamide (DMF) and propylene glycol ether (PGME) during the impregnation process The viscosity is lowered and the glass fiber reinforcement is impregnated uniformly. One large manufacturing process tower operating at 30 to 40 ft / min can use more than 3000 pounds of organic solvents per day. These volatile organic compounds are evaporated and incinerated to produce more than 3.5 million liters of CO ₂ daily. These industrial environmental and safety issues are due in part to the large amounts of organic chemicals used in the manufacture and processing of PCBs.

There are two ways to remove the solvent or VOC from the preparation of the prepreg. Melt impregnation, the first method, is commonly used in the processing of carbon fiber reinforced composites in the aerospace and aviation industry. S. R. Lycr and D. Shirrell (US Pat. No. 5,478,599) disclose techniques developed for producing electronic prepregs using a melt impregnation process. However, this method requires new tools and is difficult to use in existing treatment towers.

The prior art used organic solvents to make prepregs. All organic solvents are toxic to life in the form of concentrates used for coating. They remove fat from the skin of humans in contact, remove the protective layer, and indirectly can also cause skin redness, rashes and even aggravate inflammation caused by external influences of atmospheric reagents, chemical toxic substances, bacteria or fungi. have. Inhaled solvent vapors affect the circulation, nervous system, lungs, and liver in different ways depending on the type of solvent.

At present, in view of occupational hygiene aspects, it is necessary to reduce the amount of solvent used in coatings and replace them if possible. Ecologically, solvent vapors form smog and destroy forests.

Thus, there is a need for a solvent-free alternative method that eliminates the health risks associated with VOCs using aqueous resin emulsions without the need to use organic solvents in the preparation of prepregs, as well as eliminates the fire hazards associated with flammable solvents.

1 is a schematic of the process of the present invention using a treatment tower.

2A, 2B, 2C and 2D show sequential steps of preparing prepreg from an aqueous resin.

3 is a graph showing isothermal curing of an aqueous epoxy resin emulsion showing conversion as a function of time.

4 shows the general chemical structure of the flame retardant epoxy resin composition, and also shows dicyandiamide as a curing agent and 2-methylimidazole as an accelerator.

5 is a general structural formula of bisphenol A novolac resin.

6 is a general structural formula of epoxidized cresyl novolac (ECN).

7 is a general structural formula of tetrakis (4-hydroxyphenyl) ethane.

The present invention relates to the use of an aqueous resin emulsion which does not require the use of organic solvents in the preparation of prepregs and relates to a solvent free replacement method. The use of an aqueous resin emulsion also allows the preparation of prepregs using existing tower tools and devices. The use of aqueous epoxy resin emulsions in the manufacture of printed circuit boards has enormous potential for both environment (ie pollution) and workplace stability. Aqueous epoxy resin emulsions not only eliminate the health hazards associated with VOCs, but also eliminate the fire hazards associated with flammable solvents.

The first step in the manufacture of printed circuit boards (PCBs) comprises reinforcing materials such as woven glass fabrics, woven aramid fabrics, nonwoven aramid mats, continuous or woven carbon-fiber reinforcements, such as epoxy, bismaleimide, cyanate esters, bisnadimides, di Impregnating with an aqueous emulsion resin emulsion selected from the group consisting of acetylene and mixtures thereof. The reinforcement may also be formed from woven glass materials of the type, such as E-glass, S-glass, K-glass, D-glass, and the like. The resin can also be used in other polymeric thermoplastics, for example polyarylene ether, polyarylene ether sulfones, polyarylene ether ketones, polyimides, polycarbonates, polyphenylene oxides or biological materials, for example lignin or cellulose. And may be blended or mixed with. The impregnation process using the treatment tower is shown in FIG. 1. The impregnation process requires coating the reinforcement 10 supplied to the continuous sheet or web. The reinforcing material 10 is passed through a tank 15 containing an aqueous resin emulsion. The aqueous resin emulsion impregnates the reinforcing material 10. Excess resin is removed by the measuring roller 20 which is operated while rotating in the opposite direction of the web. The impregnated reinforcement is then dried and partially cured by the heat treatment chamber 30. Heat can be obtained by convection oven, infrared radiation (IR), ultraviolet radiation (UV), high frequency energy, electron beam irradiation (E-beam) or microwave energy. Partial curing is required to form a stable, non-tacky material referred to as prepreg. As used herein, the term "prepreg" is understood to be used in the electronics industry, but "prepreg" is generally acceptable reinforcement for reinforcing materials containing or mixed with a full refill of resin prior to the molding operation As plastics, the prepregs made according to the invention act as carriers on which the resin coating is deposited and to reduce thermal expansion of the final product. The process has two stages: a first stage comprising evaporating water from the emulsion and a second stage of partially curing the resin in the desired state referred to as the B-state.

2 is a schematic diagram showing the production of prepreg from an aqueous resin emulsion. 2A shows resin spheres 44 suspended in aqueous phase 53. 2B shows coating of emulsion on woven reinforcement 60. 2C shows the coalescence of the resin particles showing the drying process during the heat treatment step of the impregnation process. 2D shows that the resin 69 film coating the reinforcement demonstrates complete coalescence of the resin particles.

Accurate control of the thermosetting resin reaction is important because additional processes are required to manufacture printed circuit boards or other electronic products. The rheology or flow properties of the prepreg is determined by the degree of thermosetting reaction. There are several factors that are important in controlling the rheology of prepregs. The two most important things about the fixed resin composition are (i) the concentration of the curing agent and accelerator and (ii) the heat treatment during impregnation. Changes in heat treatment and time are limited in manufacturing due to energy and product requirements. Therefore, the type, concentration and reactivity of the curing agent and accelerator are important. When the resin is combined with an excessive concentration of hardener or accelerator or the prepreg is exposed to excessive heat treatment, the material does not flow sufficiently during the lamination process to produce a pore-free laminate suitable for electronic components. And, if the resin is blended with an insufficient concentration of hardener or catalyst or the prepreg is not heated sufficiently during the impregnation process, the material will not be able to produce a laminate that contains excessive flow and contains the correct resin / glass composition. The process window of opportunity to manufacture high quality "in spec" prepregs is very strict.

In each experiment using the method of the present invention, the impregnated resin is co-dried and partially cured to about 25% ± 1% conversion using thermal energy by a forced air convection oven or microwave steel or a combination thereof.

A preferred heating method for using existing manufacturing equipment is a forced air convection oven.

The most energy efficient method is to use microwave radiation with precisely controlled microwave steel, or microwave radiation in combination with a forced air oven, which very efficiently couples energy to polar residues of both water and resin. Alternatively, high frequency (RF) energy can be used with microwave radiation. RF radiation is effective at removing water, but not critically less resin. Thus, in the mixing of RF and microwave energy, RF is used for the initial drying process, microwave radiation is used for the termination of drying and the B-state of the resin composition.

On the one hand, other heat sources such as infrared radiation (IF), ultraviolet radiation (UV) and electron beam irradiation can be used.

Microwave energy is used with microwave applicators, such as home microwave ovens, or microwave applicators such as more sophisticated microwave applicators such as those disclosed in US Pat. No. 5,536,921 to Hedrick et al. The microwave energy injection into the prepreg is preferably determined by monitoring the prepreg temperature and adjusting the microwave power, typically using an infrared pyrometer, to provide the desired thermal profile. Microwave forces can be adjusted immediately and such closed loop temperature control of the process is known in the art.

The change in the level of microwave power to feed back to the control circuit using the temperature of the product is due to the applicator efficiency, absorption efficiency, prepreg process speed, applicator width or length. However, it is anticipated that microwave levels of about 90 kW (915 MHz) or less may be commercially available and used depending on the geometry used.

Preferably, the frequency of the microwave energy is the ISM band, the frequency allowed to be used industrially by the Federal Trade Commission, the most useful of which are 2450 MHz, 915 MHz, and other frequencies in the range 100 MHz to 100 GHz may be used.

Similarly, high frequency energy can be used to heat the prepreg. This form of energy works similarly to microwave energy but at lower frequencies. The biggest difference between these two energies is in the form of an applicator used to deliver power to the product or to the prepreg in the case of the present invention. RF is very effective at high water content, for example in the early stages of the process. Similar temperature feedback loops can be used to control the process temperature.

Providing thermal energy to the prepreg using IR energy can be obtained in two ways. (a) heating a platen parallel to the surface of the prepreg to an electrically red high temperature to provide heat by blackbody radiation emitted by the platen; Or (b) using an IR radiation lamp that is commercially used but does not have particularly good uniformity.

IR is a relatively inexpensive method of heat supply, but the main drawback is that it is very difficult to measure the temperature of the prepreg directly in the closed feedback loop, which is substantially the IR energy emitted by the stronger platens and that emitted by the prepreg. This is because it is impossible to distinguish IR energy. Therefore, the temperature of the platen must be fixed to stabilize and the prepreg is passed through the tower. The temperature of the platen (or the force transmitted thereto) must be fixed by measuring the pickup and flow of the prepreg product, and the temperature of the platen is typically about 1800 ° F.

The composition used in the process of the present invention comprises at least 20% by weight of a continuous aqueous phase and a resin selected from the group consisting of epoxy, bismaleimide, cyanate esters, bisnanimide, diacetylene or two or more blends of these resins. It is an aqueous dispersion containing the dispersed phase containing. The composition may also comprise a curing agent comprising up to 20% non-ionic surfactant, up to 35% amine, amide, acid anhydride or phenol functional group; And 5% or less of accelerator.

Description of the Preferred Aspects

The resin used in the composition of the process of the invention is a low molecular weight monomer or oligomer. Preferred resins for use are epoxy resins. Types of epoxy used in the composition include bisphenol A-based epoxy (DGEBA); Brominated bisphenol A epoxy (Br-DGEBA); Epoxidized cresyl novolacs; Epoxidized phenol novolacs; Epoxidized reaction products of phenols and glyoxal. Other epoxy resins suitable for use are described in "Epoxy Resins: Chemistry and Technology", 2nd Edition, Editor C.A. May, Marcel Dekker, Inc. Publisher, "Encyclopedia Of Polymer Science", McAdams and Gannon, Volume 6, pp 332-382 and European Patent No. 0385149A2.

More specifically, suitable epoxy resins for use include:

A. Glycidyl ether comprising the reaction product of epichlorohydrin and a compound containing at least one hydroxyl group. Examples of compounds conforming to this description for use in accordance with the present invention are single or mixed bisphenol A epoxy resins-diglycidyl ethers of 4,4- (isopropylidenediphenol) and brominated bisphenol A epoxy resins- Isopropylidenediphenol bis (2,6-dibromophenol).

B. Epoxideized cresyl novolac prepared by glycidylation of cresol condensation obtained from acid catalyzed resination of cresol. An example of a composition consistent with this description used in accordance with the present invention is epoxidized cresyl novolac (ECN).

C. Epoxideized phenol novolac prepared by glycidylation of phenol-formaldehyde condensation obtained by acid catalyzed resination of phenol and formaldehyde. An example of a compound consistent with this description used in accordance with the present invention is epoxidized phenol novolac (EPN).

D. Reaction products of aromatic compounds (phenols, cresols, etc.) with glyoxal. Examples of compounds in this range used in accordance with the present invention are tetraglycidyl ethers of tetrakis (4-hydroxyphenyl) ethane resins.

E. Glycidylaniline Derivatives. Examples of compounds consistent with this description used in accordance with the present invention are 4,4'-methylenebis (N, N-diglycidylaniline) and N, N-diglycidylaniline.

F. bisphenol A novolac derivatives. Examples of compounds included in this range are disclosed in FIG. 5. This type of material is sold under the name "EPI REZ SU8" by Shell Chemical Company.

Flame retardancy is imparted by including about 5 to about 25% bromine by adding brominated DGEBA in the resin formulation. Bromine at a concentration of about 15-16% per 100% solids concentration must be used in the composition to obtain the UL 94V (O) flammability rating required for the electronic material. Some DGEBA-based epoxides contain less than 50% by weight of bromine, so it is not necessary to use only brominated epoxy resins. Typically resins in blends with other epoxy components confer improved mechanical properties, chemical resistance or improved thermal stability. Some resins that may be added or blended are more functional epoxides, epoxidized cresol novolacs (ECN) or other multifunctional resins such as tetraglycidylmethylenedianiline tris hydroxy phenol / methane based One of the epoxy resins. Other flame retardant compounds may also be used, such as phosphorus-containing compounds.

The composition typically contains a surfactant comprising a non-ionic alkylarylpolyether alcohol as disclosed in US Pat. No. 3,945,964, or a block copolymer of ethylene oxide and propylene oxide. Surfactants are disclosed in the aforementioned patents and US Pat. No. 5,500,461 and surfactants are disclosed in "Water Borne Coatings", K. Doren et al., Hanser Publ., New York 1994, incorporated herein by reference. . Preferred surfactants are those prepared by reacting 2 moles of polyoxyethylene glycol with 1 mole of bisphenol A having an epoxy equivalent weight of about 468 g / mol.

In the case of epoxy resins, there are several types of hardeners or hardeners that can be used. Aliphatic amine hardening agents such as dicyandiamide, ethylenediamine, diethylenetriamine, triethylenetetramine and hexamethylenediamine. Aromatic amine hardeners such as diaminodiphenylsulfone, diaminodiphenylmethane, phenylenediamine and the respective isomers. Acid anhydride hardeners such as hexahydrophthalic anhydride, methyl tetrahydrophthalic anhydride and pyromellitic dihydrate. Also phenol hardeners such as tetrabromobisphenol A and bisphenol A. There are also polyamides, polysulfides and polymercaptans.

Accelerators used with epoxy resin materials are generally tertiary amines such as benzyldimethylamine, pyridine, triethylamine, tetramethylbutane diamine, 2-methylimidazole and 2-ethyl-4-methylimidazole There is this.

As disclosed in "Epoxy Resins: Chemistry and Technology, 2nd Edition, Editor CA May, Marcel Dekker, Inc. Publisher" and "Encyclopedia Of Polymer Science", McAdams and Gannon, Volume 6, incorporated herein by reference. Like other curing agents and accelerators can be used.

Manufacturing Method of Preferred Embodiment

The aqueous epoxy resin composition used in the proof of the present invention contains a blend with a brominated and non-brominated epoxy resin with a nonionic surfactant and deionized water. The resin was combined with additional deionized water to lower the viscosity, and a hardening agent / catalyst mixture of dicyandiamide / 2-methylimidazole to promote the reaction of the epoxy moiety for a suitable temperature and time.

In the manufacture of a PCB according to the invention, the reinforcement was passed through a tank containing an aqueous resin emulsion having the composition detailed in Examples 1 and 2 below. The aqueous resin emulsion was impregnated with a reinforcing material. Excess resin is removed by a measuring roller which is operated to rotate in the opposite direction of the web. The impregnated reinforcement is then dried and partially cured by the heat treatment chamber. Heating is performed by a forced air convection oven, but the process can also be operated efficiently by microwave energy, infrared radiation (IR), ultraviolet radiation (UV), electron beam irradiation (E-beam), RF energy or IR radiation. . Partial curing is required to form a tack free stable material referred to as prepreg.

The production of high quality prepregs of 5000 feet square was achieved using a treatment tower. For the brominated epoxy emulsion, the temperature and time required for the B-state, the prepreg was found to be comparable to the conventional methyl ethyl ketone solvent prepared FR-4 epoxy resin system.

A plot showing the isothermal cure aspect of the brominated epoxy resin emulsion at 150 ° C. is shown in FIG. 3. The target conversion of the in-spec prepreg to obtain flow properties suitable for lamination is 27 ± 2%. The conversion at 150 ° C. as a function of time is relatively fast, especially at 20 to 80% as observed in the curve slope of FIG. 3. This indicates that the process window for making in-spec prepregs is narrow and requires precise process control.

Table 1 shows the temperature, adhesion, and water absorption of the aqueous resin and laminates prepared from the comparative methyl ethyl ketone processed FR-4 resin (ie, fully cured composites). The glass transition temperature, Tg and decomposition temperature, Td for the two resin systems are similar but not exactly the same as expected, due to variations in the structure and molecular weight of the initial epoxy resin component. As shown in Table 1, the water uptake for three different exposure conditions is also comparable.

The adhesion of the aqueous epoxy resin to the oxide treated copper foil and silane treated copper foil was slightly improved compared to the FR-4 resin control as shown in Table 1. Self-adhesion (ie adhesion between two layers of prepregs in the laminate) as measured by interlaminate bond (ILB) strength was much better than the comparative FR-4 resin. All failures were tacky (i.e. at the resin / resin interface), indicating good glass / resin adhesion. These results suggest that the adhesion is independent of whether the prepreg was prepared from an organic solvent or an aqueous emulsion.

Example 1

An aqueous epoxy based DGEBA resin used for the demonstration of the present invention was obtained from Shell Chemical Company as supplier number CMD W6045201. The general chemical structure of the composition is shown in FIG. 4 with dicyandiamide as the curing agent and 2-methylimidazole as the accelerator. The surfactant was added in advance by the supplier. The viscosity was reduced by the addition of deionized water. The curing agent / catalyst mixture of dicyandiamide / 2-methylimidazole was dissolved in deionized water before mixing with the resin, respectively. The formulation consisted of 0.4 part (phr) of 2-methylimidazole and 5 phr of dicyandiamide per 100 parts. The blended mixture was mixed for 1 hour using mechanical agitation before use. 4 L of the combined mixture was added to the treatment tower tank. The tropical convection oven was preheated to 150 ° C. Woven 106 style glass fiber cloth (13 inches wide) was used as reinforcement. The web speed was fixed at 6 feet / minute. The reverse rotation measurement roller was fixed at 1.5 feet / minute. The resulting prepreg was transparent and exhibited a cure conversion of 25 to 29%.

Example 2

The prepreg prepared in Example 1 was laminated using a high pressure hydraulic press using an electric platen. Ten prepreg layers were stacked between two surface-treated Cu foils. Lamination conditions consisted of raising the temperature from room temperature to 177 ° C. at a rate of 10 ° C./min. The pressure used during lamination was 300 lb / in ² (psig). The stack was held at 177 ° C. for 90 minutes and then cooled at a rate of 4 ° C./min. Copper skin measurements and interlayer bond measurements were performed according to the specifications disclosed by IPC (Test Method IPC-TM-650).

The results of the processes described in Examples 1 and 2 are shown in Table 1.

exam H ₂ O resin FR-4 resin Temperature (℃) T _g 125 128 T _d 302 312 Coupling Force (lbs / in) Oxidized Copper 12.2 11.3 Silane-treated copper 10.6 9.7 ILB 13.2 10.3 Water absorption (%) 24 hours, room temperature 0.21 0.35 17 hours, boiling water 2.92 2.17 1 hour 135 ℃ / relative humidity 85% 1.62 1.72

Example 3

A nonionic aqueous epoxy resin emulsion (FIG. 5) based on bisphenol A novolac was used for illustration purposes. Surfactant was added beforehand in Shell Chemical Company. The composition supplied contained 5 wt% surfactant, 50 wt% resin and 45 wt% deionized water. A curing agent / promoter mixture of dicyanodiamide (DICY) / 2-methylimidazole (2MI) was used. The concentrations of DICY and 2MI were systematically varied to determine their effect on chemical reaction rates. The water concentration of the starting aqueous epoxy resin emulsion was increased from 45% to 54%. Additional deionized water needed for dilution was heated to 40 ° C. and DICY and 2MI were added.

Upon dissolution, water, DICY, 2MI mixture was added to the starting epoxy resin emulsion with mechanical stirring.

The reaction rate was monitored by a differential scanning colorimeter. Samples were prepared using variable amounts of DICY and 2MI. The sample was then poured onto a Petri dish and dried under vacuum at 40 ° C. for 24 hours. To simulate a typical manufacturing drying / curing B stage cycle for prepregs prepared in a treatment tower, samples were heat treated at 100 ° C. for 5 minutes in a forced air convection oven. The conversion was then measured by the following equation:

Conversion rate = ΔH _unheated -ΔH _heated / ΔH _unheated

Wherein ΔH _unheated (x100) is an absolute value since the calorific value of the polymerization reaction under non-heat treatment is negative and is negative; ΔH _heating is the value for the sample heated to 160 ° C. for 5 minutes.

Table 2 illustrates the effect of accelerator (2MI) concentrations on a constant DICY concentration of 4% by weight (weight based on epoxy resin weight).

DICY Concentration (%) ^* 2-MI (%) ^** Conversion rate% ^** 4 0.2 13 4 0.4 28 4 0.6 33 ^* Based on the weight of epoxy resin. ^** After step B at 160 ° C. for 5 minutes.

Table 3 describes the effect of curing agent (DICY) concentrations varying with 2MI concentrations of 0.2 wt%, 0.4 wt%, and 0.8 wt% (based on epoxy resin weight).

DICY Concentration (%) ^* 2-MI concentration (%) ^* Conversion rate% ^** 4 0.2 13 8 0.2 33 4 0.4 28 8 0.4 - 4 0.8 33 8 0.8 41 ^* Based on the weight of epoxy resin. ^** After step B at 160 ° C. for 5 minutes.

Example 4

The composition described in Example 1 (known herein as bromine epoxy) resulted in a material having a glass transition temperature of 125 ° C. described in Table 1. To achieve higher glass transition temperatures, the composition was remixed by the addition of epoxidized cresyl novolac (hereafter ECN) as shown in FIG. 6006-W-70). ECN was determined from bisphenol A novolac as shown in FIG. 5 (shell chemical feed number EPI-REZ 5003-W-55) and tetraglycidyl ether of tetrakis (4-hydroxyphenyl) ethane as shown in FIG. From then it was blended with tetra epoxy). This composition has a shell chemical feed number Epon 1031. The results of the recombination are described in Table 4.

The curing agent (DICY) and accelerator (2-MI) were kept constant at 4% and 0.5% by weight for each composition based on the total epoxy weight.

In order to maintain sufficient antiflammability properties to achieve UL 94V (O) ignition rates, a minimum bromine concentration of about 15% by weight (based on total epoxy weight) should be maintained in the final cured resin.

From Table 4, it is clear that increased glass transition temperature is achieved by changing the weight of the epoxy resin. The concentration of tetra epoxy was maintained at 6% and used as dye for the photolithography process. By increasing the amount of ECN and bisphenol A novolac, the glass transition temperature increased significantly from 124 ° C to 148 ° C. Moreover, flame resistance was preserved by maintaining a minimum bromine concentration of 15%.

Bromine epoxy ECN Vis A Novolak Tetra epoxy ^* T _g ^** Bromine (%) ^*** 100 0 0 0 124 20+ 84 5 5 6 141 16.8 80 7 7 6 144 16.0 78 8 8 6 148 15.6 ^* Based on the weight of epoxy resin. ^** Glass transition temperature measured by DSC after curing at 175 ° C. for 2 hours. ^*** Calculation

By removing the organic solvent from the manufacturing process as described in the embodiments disclosed above, there are significant environmental benefits. In a typical manufacturing process tower, a large amount of volatile organic compounds (VOCs) such as acetone, methylethyl ketone, toluene, methyl cellosolve, dimethylformamide propylene glycol ether and the like for lowering resin viscosity and for uniform incorporation of glass fiber reinforcement Propylene glycol monomethyl ether acetate is used. A single large manufacturing process tower operating at 30-40 ft / min can use more than 3000 lbs of organic solvent per day. The vaporization and incineration of these volatile organic compounds generates more than 3.5 million liters of carbon dioxide per day. This is for a single tower; Some plants have more than 25 towers operating simultaneously. Some argue that this can have a significant environmental impact on the "greenhouse effect".

Using the aqueous resin of the present invention there is no VOC emission. This eliminates the need for incinerators and can significantly reduce carbon dioxide.

Removal of organic solvents can also reduce process waste (ie contaminants) that are typically incinerated or landfilled. In addition, the aqueous process creates a safer working environment by eliminating human exposure to VOCs and eliminating the fire hazards created by commonly used flammable solvents such as acetone and methyl ethyl ketone. In terms of cost, the aqueous process reduces safety costs by improving workplace safety (chemical exposure) and eliminating the need for halon fire suppression and foam systems.

Moreover, aqueous processes are important for product performance. That is, this makes it possible to use hardeners such as dicyanodiamide which have been removed in advance because of the safety concerns of the solvents (glycol ethers) required for the preparation.

Example 5

Prepregs were prepared using the compositions shown in Example 1 using microwave energy successfully. As in conventional prepreg manufacture, a continuous woven glass web is passed through a dip tank containing emulsified resin and a set of counter rotating measuring rollers to remove excess resin and to suppress resin consumption by the web. I was. When the web passes through the measurement roller, the web has a white appearance due to the uniform coating of the glass cloth emulsion. After passing the metering roller, the web is passed through the predrying chamber for about 50 seconds. Optionally, hot air can be used in the predrying zone to initially remove water from the fibers. Although some water was removed from the predrying chamber, the prepreg retained its white opaque appearance before entering the microwave applicator. It is not necessary to use a predrying chamber.

The microwave applicator consists of four different microwave cavities operating in TM mode at 2.45 GHz (total microwave energy was 2.2 kW for a 12 inch wide web). Temperatures at four different points in the process were measured by IR pyrometer. The temperature was then adjusted by varying the microwave intensity in each cavity until the desired temperature profile was obtained. Typical preferred temperature profiles consist of 130, 130, 190, 200 ° C. at the center of each applicator. After leaving the microwave applicator, the web was rapidly cooled to ambient temperature to stop the progress of curing. Prepregs are slightly transparent, light yellow indicators of in-spec prepregs. The test revealed a very uniform conversion of the epoxy resin with no bubbles or voids across the width of the prepreg.

Accordingly, various omissions, substitutions, and changes in the form and details of the methods and combinations of the present invention and the processes indicated and indicated, indicated and pointed to fundamentally novel features of the present invention as applied to the preferred embodiments of the present invention Of course, it can be carried out by those skilled in the art without departing from the spirit of the invention. In addition, it is also to be understood that the drawings need not be drawn to scale and are merely conceptual in nature. The present invention is not limited by the above-described embodiments represented by the examples, but may be modified by various methods within the scope of protection defined by the appended claims.

The present invention produces prepregs with the same level of B-state curing and comparable fluidity and moisture absorption without the use of organic solvents that adversely affect the environment and the body.

Claims (18)

Passing a continuous reinforcement in the form of a sheet or web through a container containing an aqueous emulsion resin to form an impregnated reinforcement; Passing the impregnated reinforcement into means for evaporating water from the emulsion in the reinforcement; And Partially curing the impregnated reinforcement to form a prepreg material. The method of claim 1, The impregnated reinforcement is added to a means for removing excess resin prior to evaporating the water. The method of claim 1, And the continuous reinforcement sheet or web is selected from the group consisting of woven glass fabrics, woven aramid fabrics, nonwoven aramid mats, continuous carbon-fiber reinforcements and woven carbon-fiber reinforcements. The method of claim 1, The aqueous emulsion resin is a method for producing a prepreg component selected from the group consisting of epoxy, bismaleimide, cyanate ester, bisnadeimide, diacetylene, aqueous polytetrafluoroethylene and derivatives, polynorbornene and blends thereof . The method of claim 4, wherein A method for producing a prepreg component which blends the resin with a polymerizable thermoplastic. The method of claim 4, wherein The manufacturing method of the prepreg component which blends the said resin with an inorganic fine particle. The method of claim 4, wherein A method for producing a prepreg component which blends the resin with a biological material. The method of claim 4, wherein A method for producing a prepreg component, wherein the resin comprises an epoxy material. The method of claim 8, A glycidyl ether wherein the epoxy material comprises a) a reaction product of a compound containing epichlorohydrin and at least one hydroxy group; b) epoxidized cresyl novolac; c) epoxidized phenol novolacs; d) reaction products of aromatic hydroxyls and glyoxal; e) glycidylaniline derivatives; Or f) a bisphenol A novolak derivative. The method of claim 9, The epoxy material is diglycidyl ether of 4,4- (isopropylidenediphenol); Isopropylidenediphenolbis (2,6-dibromophenol); Epoxidized cresyl novolac prepared by glycidylation of cresol condensates obtained from acid catalyzed resination of cresol; Epoxidized phenol novolacs prepared by glycidylation of phenol-formaldehyde condensations obtained from acid catalyzed resination of phenols and formaldehyde; Bisphenol A novolac; Tetraglycidyl ether of tetrakis (4-hydroxyphenyl) ethane resin; A method for producing a prepreg component selected from the group consisting of 4,4'-methylenebis (N, N-diglycidylaniline) and N, N-diglycidylaniline. The method of claim 9, A method for producing a prepreg component, wherein the epoxy material contains a curing agent selected from the group consisting of aliphatic amine curing agents, aromatic amine curing agents, acid anhydride curing agents, and phenol curing agents. The method of claim 11, A method for producing a prepreg component wherein the epoxy material is prepared using a tertiary amine catalyst. The method of claim 12, A method of producing a prepreg component wherein said aqueous epoxy resin is dispersed in deionized water containing a non-ionic surfactant. The method of claim 13, The continuous aqueous phase is at least 25% water and at least 20% resin; Up to 20% non-ionic surfactant; Up to 35% curing agent; And 5% or less of accelerator. The method of claim 14, The composition comprises 20 to 30% brominated bisphenol A epoxy resin and 20 to 30% bisphenol A epoxy resin, the curing agent is dicyandiamide and the promoter is 2-methylimidazole. . The method of claim 14, And means for evaporating and partially curing water from the impregnated reinforcement. The method of claim 16, And said means is selected from the group consisting of UV, IR, hot air, microwave, RF, and combinations thereof. A continuous reinforcement in the form of a sheet or web selected from the group consisting of a woven glass fabric, a woven aramid fabric, a nonwoven aramid mat, a continuous carbon-fiber reinforcement and a woven carbon-fiber reinforcement is passed through a container containing an aqueous emulsion resin to impregnate the impregnated reinforcement. Forming, wherein the resin is selected from the group consisting of epoxy, bismaleimide, cyanate ester, bisnanimide, diacetylene, aqueous polytetrafluoroethylene and derivatives, polynorbornene, and blends thereof; And Passing the impregnated reinforcement through a means for evaporating water from the emulsion in the reinforcement and partially curing the impregnated reinforcement to form a prepreg material, wherein the means is UV, IR, hot air, microwave, RF And it is selected from the group consisting of a combination thereof).