EP0779900A1

EP0779900A1 - Flame resistant single-component reaction resin

Info

Publication number: EP0779900A1
Application number: EP95929754A
Authority: EP
Inventors: Winfried Plundrich; Ernst Wipfelder
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1994-09-06
Filing date: 1995-09-05
Publication date: 1997-06-25
Also published as: US5804680A; DE4431751C1; WO1996007678A1; JPH10505122A

Abstract

A single-component reaction resin hardenable by UV radiation consists of (A) a phosphorus-containing acrylate; (B) another unsaturated compound that may be radically copolymerised with acrylates; and (C) a radical photo-initiator system. Various simple ways of producing phosphorus-containing acrylates are disclosed. These acrylates may in turn be mixed with the most different commercially available acrylate components to form storage-stable reaction resins. These resins are useful for masking electronic components and may be completely hardened by UV radiation into a flame-resistant masking material.

Description

description

Flame-retardant one-component reaction resin.

Processing-friendly, environmentally compatible and flame-retardant reactive resin molding materials are required for covering or encapsulating electronic components. Both for reasons of processing security and for economic reasons, there is an increasing demand for single-component reactive resins which are stable in storage at room temperature for at least three months and which can be cured in a short time at relatively mild curing temperatures of, for example, 100 ° C. . A further requirement for reactive resins that can be used for this purpose, or the molding materials produced from them, is corrosion-free behavior, which does not impair the function and thus the service life of a component covered thereby. The desired flame retardancy should be such that the reactive resins or the molding materials produced therefrom can be easily reused or at least disposed of without problems.

A reaction resin system which contains phosphorus-containing reactive compounds to improve the flame resistance is known from EP-A 41 24 25. By reacting a hydroxy-functional phosphorus compound with an organic anhydride, an acidic ester is obtained which can serve as a phosphorus-containing hardener component for a two-component reaction resin based on epoxy.

A one-component phosphorus-containing reactive resin system is known from WO 94/10 223, which is UV-initiated curable. The glycidyl ester of a phosphorus-containing acid serves as the phosphorus component, which together with common epoxy resins and a photoinitiator results in a one-component reaction resin system for a cationic curing process, which shows sufficient storage stability and good corrosion behavior.

EP-A 278 029 discloses phosphorus-containing unsaturated compounds which are proposed for coating metals and for use as adhesives. Alkali and alkaline earth metal salts are contained as catalysts for thermal curing. This affects their usability for electronic components.

Unsaturated phosphorus-containing carboxylic acid derivatives are known from DE 20 52 569. These can be converted into copolymers in acidic form with other monomers.

From DE-A-32 07 504 a photosensitive resin composition is known which contains a phosphate compound with a photopolymerizable unsaturated bond in combination with a heteroaromatic such as benzotriazole.

It is therefore an object of the present invention to provide a further ready-to-use reaction resin which is stable in storage for several months at room temperature and which can be fully cured at moderate temperatures up to about 100 ° C. and which is simple to use with apparatuses customary for casting resins can be processed and which is curable to form materials which have sufficient flame retardancy required for electronic components and show good corrosion behavior.

This object is achieved according to the invention with a reactive resin system according to claim 1. Further refinements of the invention can be found in the subclaims.

For the reactive resin system according to the invention, a number of phosphorus-containing acrylates are proposed which can be easily prepared from common and reactive phosphorus compounds. The phosphorus-containing acrylates can be combined with commercially available acrylates or epoxy acrylates and a photoinitiator system to form the reaction resin system according to the invention. This is stable for at least six months at room temperature. It can be applied easily and without solvents using application devices known for casting resins and has, for example, a viscosity of from 1000 to 5000 Pas at 60 ° C. It shows good corrosion behavior on electronic components.

The reaction resin system can be cured in a maximum of two minutes by means of UV radiation. The phosphorus-containing acrylates, or the phosphorus contained therein, have no adverse effect on the curing reaction.

Adequate flame resistance can be achieved by setting a sufficiently high phosphorus content of, for example, 1 to 5 percent by weight, preferably 1.5 to 3 percent by weight. The UL 94 V0 standard from Underwriters Laboratories is met in one embodiment up to a sample thickness of 1.6 mm.

By adding fillers and selecting suitably coordinated acrylates, a wide range of properties can be achieved with the reactive resin system. For example, the flame resistance can be further improved by admixing suitable fillers such as, for example, aluminum hydroxide or magnesium hydroxide.

The thermal reactivity can be modified by admixing thermally activatable radical initiators, for example organic peroxides. Thus, even those areas of a reaction resin applied to a component can be completely hardened by a thermal aftertreatment, which are shaded from UV radiation. Such shaded areas would otherwise be after the Irradiation have an incomplete curing and thus lead to inhomogeneities that could impair the properties of the components covered or encapsulated with it. In order not to deteriorate the storage stability due to the thermally activatable radical initiator, organic peroxides with a decomposition temperature of preferably above 100 ° C. are selected.

The thermal / mechanical properties can be advantageously influenced by suitable selection of the phosphorus-containing acrylates (component A) and the further unsaturated compounds (component B). A higher mechanical strength and a higher glass transition temperature are achieved by using highly functional acrylates or copolymerizable unsaturated compounds, so-called cross-linking enhancers or reactive thinners, which increase the cross-linking density in the reaction resin material. Improved flame retardancy is achieved by using components with a high proportion of aromatic groups.

A first way of obtaining phosphorus-containing acrylates is to react a hydroxy-functional phosphorus compound I with an isocyanatoalkyl (meth) acrylate II

R _n -P (-R - OH) $ - _n + (3 - n) OCN - alkylene - O - C - CR * = C # 2 I II

0 0 Q

→ R _n -P / {- R - 0 - Cn - NH - alkylene - 0 - \ C \ - CR * = CH2) 3- _n

Mean: n = 0 or 1

R * alkyl or aryl; R: - (CH -) κ ^with K = 1 to 5,

-0- (CH2-) _m π tm = 1 to 5 or (CH ₂ -) _p -CH2 - W < _{(C 2} _ ₎ with p = 1 to 4;

R *: hydrogen or methyl.

Instead of the isocyanatoalkyl (meth) acrylate ^ 1, the reaction can also be carried out with methacrylic acid isocyanate IX.

0 CH ₃

IX II / ³

OCN - C - C = CH ^■ 2

The reaction, with or without solvent, takes place in a stoichiometric ratio, whereby a urethane-bridged phosphorus (meth) acrylate is formed.

Another possibility for producing a phosphorus-containing acrylate is to react a phosphorus-containing epoxide III with a hydroxy-functional acrylate, for example a hydroxyalkyl (meth) acrylate IV.

0 0 O

, ny \ "ii _*

R _n P - (OCH2CH - CH2> 3_ _π + (3 - n) HO - alkylene - 0 - C CR = CH2

in rv

O OH O

. n 1 11 *

→ R _n P - {OCH2 CH - CH2O - alkylene - 0 - C CR = Ctf2) 3-.n

Mean: n = 0, 1 or 2; R ': alkyl or aryl; R *: hydrogen or methyl.

The phosphorus-containing epoxides can be esters such as, for example, glycidyl esters of phosphonic acid. The hydroxy-functional acrylate preferably has a primary OH group in order to do justice to the lower reactivity of the phosphorus-containing epoxy compound. The mono- or di-glycidyl compounds are preferably reacted with mono- to tri-hydroxy compounds. A strong catalyst No acid is required, for example a hexafluoroantimonate in a concentration of 0.1 to 5 percent by weight, preferably 0.2 to 1 percent by weight. A stopper for the catalyst must be added to the phosphorus-containing acrylate obtained in this way for reasons of storage stability. The appropriate amount of an amine is added to the reaction resin system to completely neutralize the acid. Thereafter, neither the catalyst nor the stopping agent have a negative influence on the storage stability or reactivity of the reaction resin system.

In addition, phosphorus-containing acrylates can be prepared by reacting glycidyl esters of phosphoric acid III with (meth) acrylic acid.

Another possibility of representing phosphorus-containing acrylates consists in reacting a hydroxyalkylphosphorus compound 1 with a reactive (meth) acrylic acid derivative V

0 0

(3 - n) R 'CH = CR * Cn - X + R _n - P «(-R - OH) - _n

0 0

II II

→ R _n - P (-R - O - C - CR = CH - R ') 3_ _π

where X is halogen and n is 0 or 1. R 'is also alkyl or aryl or R * is hydrogen or methyl. Care must be taken during the reaction that the hydrohalic acid formed is trapped by a suitable base, for example by adding an amine. The resulting ammonium halide compound can then be precipitated and separated if necessary.

The invention is explained in more detail below on the basis of exemplary embodiments. A) Exemplary embodiments of phosphorus-containing acrylate components

example 1

A phosphorus-containing acrylate component VI is produced by reacting sec-butyl-bis (3 hydroxypropyl) phosphine oxide and isocyanatoethyl methacrylate:

CH'X 0 O CH'X

I II "II H3CH2 CH - P (-CH2CH2CH20H) 2 + 2 OCN - CH2CH2O - C - C = C # 2

CH'X 0 0 0 CH'X

I ^J I II »→ CH3CH2 CH - P {-CH2CH2CH2 - O - C - NHCH2CH2O - C - C = 0-2) 2

VI

In a 3-neck flask equipped with a paddle stirrer, thermometer and drying tube, filled with drying agent (calcium oxide), 40 parts by mass (0.18 mol) of sec-butyl bis (3-hydroxypropyl) phosphine oxide and 40 parts by mass dried dichloroethane is diluted, introduced and, with exclusion of moisture, 55.84 parts by mass (0.36 mol) of isocyanatoethyl methacrylate are added dropwise with stirring using a dropping funnel. The reaction temperature should not rise above 25 ° C, otherwise a slight cooling (water bath) is required. After a reaction time of 2 hours, the solvent is removed under vacuum at a bath temperature of max. 50 ° C. quantitatively removed, 4.8 parts by weight of hydroxyethyl methacrylate (0.04 mol) then being added to stop any isocyanate groups still present. The product Vi has a viscosity of 750 mPas at 60 ° C., a phosphorus content of 5.5 percent by mass and results in a storage capacity at room temperature of more than 6 months. Refrigerator storage increases shelf life to more than 1 year. Example 2

Production of a phosphorus-containing acrylate compound by reacting an epoxy-containing phosphorus compound with a hydroxyalkyl methacrylate.

Another phosphorus-containing acrylate VII is produced by reacting phenylphosphonic acid diglycidyl ester with an excess of hydroxyethyl methacrylate.

0 0 0 CH'X

W / \ "II l

CH ( _f - P (-OCH2CH - CH2> 2 + 2 HOCH2CH2O - C - C = C # 2 →

O OH 0 CH'X

AI II \ ⁵

C6 «6 ^{- p} (-O H2 CH CH2 - OCH2CH2O - C - C = CH2> 2

VII

30.92 parts by mass (0.238 mol) of hydroxyethyl methacrylate (slight excess) and 0.31 parts by mass of hexafluoroantimonic acid (1 mmole) are placed in the apparatus described in Example 1 and 31.0 parts by mass (0.115 mol) of phenylphosphonic acid diglycidyl ester are added dropwise over an hour ¬ ben. The reaction mixture is stirred for 45 hours at room temperature and then for 20 min. heated to 60 ° C. Thereafter, 0.3 parts by mass (2 mmol) of 2-diisopropylaminoethanol are added to the reaction mixture to neutralize the catalyst and another 5 min. treated at 60 ° C. The epoxy value determination carried out on this shows a 99% reaction conversion.

Product VII has a viscosity at 25 ° C of 14000 mPas, has a phosphorus content of 5.6 percent by mass and shows a storage stability of more than 1 year at room temperature.

Example 3 Reaction of a hydroxyalkyl phosphorus compound with a reactive methacrylic acid derivative.

A phosphorus-containing acrylate VIII is obtained by reacting sec-butyl-bis (3-hydroxypropyl) phosphine oxide with methacrylic acid chloride

c « ₃ gc« ₃ o

CH-pH2 CH - P (CH2CH2CH2θH) 2 + 2 # 2 = - C - Cl →

H O O CH'X

I H, H>

CH3CH2 CH - P {CH2CH2CH2O - C - C = Ctf2) 2

VIII

In a 3-neck flask equipped with a paddle stirrer, thermometer and a drying tube filled with calcium oxide, 44.45 parts by weight (0.20 mol) of sec-butyl-bis (3-hydroxypropyl) phosphine oxide, 41 , 48 parts by weight (0.41 mol) of triethylamine (slight excess) and 60.0 parts by weight of dried toluene and 41.82 parts by weight (0.40 mol) of methacrylic acid chloride and 40.0 parts by weight of dried toluene are added dropwise with constant stirring using a dropping funnel admitted. The reaction vessel is cooled with a Kryomat. The reaction temperature should not exceed 5 ° C. To complete the reaction, the reaction mixture is further treated at room temperature for 10 hours.

The precipitated amine hydrochloride is then separated off using a suction filter, the filtrate is shaken out three times with water, separated off and the organic phase is dried using sodium sulfate.

The solvent toluene and any triethylamine still present are removed in a rotary evaporator under vacuum at a bath temperature of max. 50 ° C removed quantitatively. For better storage stability, 0.008 parts by weight of hydroquinone are added. Product VIII has a viscosity of 400 mPas at 25 ° C.

Example 4

43.05 parts by weight of the phosphorus-containing acrylate component VI described in Example 1 become 29.49 parts by weight

® Bisphenol-A-epoxyacrylate (Ebercryl 600), 5.9 parts by weight of reactive thinner trimethylolpropane triacrylate, 0.39 parts by weight of 2-methyl-l- [4 (methylthio) -phenyl] -2-morpholinopropanone-l

® (Irgacure 907), 0.39 parts by weight of isopropylthioxanthone

® (Quantacure ITX), 0.78 parts by weight of a peroxide (Luperox

® ®

231-50) and 20.00 parts by weight of aluminum hydroxide (Apyral 4) mixed to a homogeneous mass.

A mass which is stable at room temperature and has a viscosity of 1240 mPas at 60 ° C. is obtained. It shows good workability.

Brief UV radiation of 30 seconds can be used to produce moldings in layers up to 1 cm thick. With the help of a thermal aftertreatment of 30 minutes at 130 ° C, any layer thicknesses can be cured completely. The hardened molding material meets the UL 94 VO standard from Underwriters Laboratories up to a sample thickness of 1.6 mm.

Example 5

41.67 parts by weight of the acrylate component VI with 36.76 parts by weight of an acrylate-containing epoxyphenol novolak

(Ebecryl 639®) - 100 parts by weight of Ebecryl 639® contain 30 parts by weight of trimethylolpropane triacrylate and 10 parts by weight of hydroxyethyl methacrylate - 0.39 parts by weight of 2-methyl-l-

[4 (methylthio) phenyl] -2-morpholinopropanone-1 (Irgacure 907®), 0.39 parts by weight of isopropylthioxanthone (Quantacure ITX® ⁾ , 0.78 parts by weight of a peroxide (Luperox 231-50®) and 20.00 parts by weight of aluminum hydroxide (Apyral 4®) mixed to a homogeneous mass at 60 ° C. The cast resin formulation has a viscosity of 1400 mPas at 60 ° C and a storage stability of 1 year at room temperature.

After mixing and degassing, this casting resin is poured into a correspondingly flat casting mold, UV-exposed for 60 seconds (intensity of the UV lamp 50 mW / cm ² ) and then subjected to a thermal aftertreatment at 120 ° C. for 1 hour.

Standard test rods produced in this way are subjected to flame retardancy testing in accordance with Underwriters Laboratories UL 94 VO. The cast resin molding material according to the invention fulfills the

Flame resistance specification up to a sample thickness of 3.2 mm and shows good mechanical and chemical molding properties.

The phosphorus-containing acrylates VII and VIII can be mixed in an analogous manner with the other resin components to form ready-to-use reactive resins, which in turn have high storage stability, a sufficiently low viscosity for casting resin applications and easy hardenability to form flame-retardant molding materials.

Claims

claims

1. Flame-retardant one-component reaction resin with the components that can be processed as casting resin and curable by radiation

A) a phosphorus-containing acrylate, which is obtained as a product of one of the following reactions

AI) a hydroxyalkyl phosphorus compound 1 with an isocyanatoalkyl (meth) acrylate ^ 1

0 II

IR _n - P {-R - OH) $ - _n or

(n = 0.1)

A2) a hydroxyalkyl phosphorus compound 1 with a methacrylic acid isocyanate IX

CH ₃ 0 I II IX CH, = C - C - NCO

A3) an epoxy-containing phosphorus compound III with a hydroxyalkyl (meth) acrylate IV

O 0

III 0 / \ (n = 1, 2)

R _n -P (-0 - R - CH - CH ₂ ) 3_ _π

0

IV HO - alkylene - 0 - C - CR ^* = CH ₂ or

A4) a hydroxyalkylphosphorus compound I with a reactive (meth) acrylic acid derivative V 0

R '-CH = CR

where applies

R '= alkyl or aryl;

R = alkylene radical;

R * = H or methyl; X = halogen and

B) a further unsaturated compound which can be radically copolymerized with acrylates and

C) a radical photoinitiator system, the reaction resin being solvent-free and having a phosphorus content of 0.5-5% by weight (based on the sum of components A to C).

2. Reaction resin according to claim 1, in which a thermally activatable radical starter is contained as further component D.

3. Reaction resin according to claim 1 or 2, in which, as a further component E, a mineral filler is contained in a proportion of up to 60 percent by weight.

4. Reaction resin according to one of claims 2 or 3, which contains as an activatable radical initiator D an organic peroxide with a decomposition temperature of preferably ≥ 80 ° C.

5. Reaction resin according to one of claims 1 to 4, in which component B is selected from (meth) acrylates, epoxides esterified with (meth) acrylic acid and low-molecular-weight reactive diluents based on acrylate.

6. Reaction resin according to one of claims 3 to 5, which contains aluminum hydroxide as filler (component E).

7. Use of a reaction resin according to one of claims 1 to 6 for covering electrical and electronic components.