Silicon-lactam blends and products obtained therefrom

Crosslinkable polyamide blends are provided of lactam, a silicon substituted lactam and a base polymerization catalyst. The crosslinkable blends can be reinforced and converted to polyamide parts by standard molding techniques.

CROSS REFERENCE TO RELATED APPLICATIONS 
Reference is made to copending applications Ser. No. 645,638, for Silyl 
Polyamides and Method for Their Preparation, filed Aug. 30, 1984 of 
Policastro et al. and Ser. No. 752,744, for Thermoplastic-Polyamide 
Copolymers and Blends, filed July 8, 1985 of Chao et al. 
BACKGROUND OF THE INVENTION 
Prior to the present invention, crosslinked nylon compositions were 
prepared by anionic polymerization of a lactam utilizing an epoxy 
component in the presence of a basic catalyst and a promoter, as shown by 
Yang, U.S. Pat. No. 4,400,490. Although the nylon compositions of Yang 
provide useful RIM materials resulting in the production of a variety of 
valuable molded products, the Yang compositions are primarily a 
two-component system of lactam and epoxy resin. The two-components mixture 
must be utilized immediately after mixing to achieve effective results. 
The present invention is based on the discovery that anionic polymerization 
of lactams can be achieved resulting in the production of crosslinked 
polyamide, or reinforced crosslinked polyamide using certain lactam 
promoters having silicon attached to the lactam nitrogen by 
silicon-nitrogen linkages, as defined hereinafter. The base catalyzed 
crosslinkable blends of lactam and silicon substituted lactam are 
convertible to high molecular weight polyamide upon heating. In addition, 
reinforced crosslinked polyamide can be made by incorporating into such 
silicon-lactam blends, high performance aromatic thermoplastic polymers, 
such as polyarylene oxides, polyarylene sulfones and polyarylene esters, 
or inert materials, such as glass fiber or reinforcing silica. 
STATEMENT OF THE INVENTION 
There is provided by the present invention, a heat curable 
silicon-containing lactam blend selected from the class consisting of 
(A) a blend comprising, 
(i) 0.01 to 100 mole percent of silicon-lactam and 99.99 to 0 mole percent 
of lactam and 
(ii) an effective amount of a Group I material, and 
(B) a blend comprising 
(iii) a mixture of lactam, and 0.01 to 1 mole, per mole of lactam of a 
lactam silylating agent which is free of lactam groups attached to silicon 
by carbon-silicon linkages selected from organosilazanes, and 
organosilicon material selected from silanes and polydiorganosiloxanes, 
which organosilicon material has at least one labile monovalent radical 
attached to silicon selected from the class consisting of halogen and a 
monovalent group attached to silicon through an oxygen or nitrogen linkage 
and is capable of silylating lactam at a temperature of 140.degree. C. to 
350.degree. C., and 
(iv) an effective amount of a Group I material, 
and the silicon-lactam of (A) has at least 1 silicon atom attached to a 
lactam ring by a silicon-nitrogen linkage selected from the class 
consisting of silanes, organosiloxanes, cycloorganosiloxanes, 
organopolysilanes, polysilalkylenes, polysilarylenes, organosilazanes and 
cycloorganosilazanes. 
There is also provided by the present invention a method for making 
crosslinked polyamide compositions which comprises heating the above 
defined heat curable silicon-containing lactam blends at a temperature in 
the range of between 140.degree. C. to 350.degree. C. 
Lactam which can be utilized in the practice of the present invention is 
included by the formula 
##STR1## 
where R and R.sup.1 are members selected from the class consisting of 
hydrogen, C.sub.(1-8) alkyl, substituted C.sub.(1-8) alkyl, C.sub.(6-13) 
aryl, substituted C.sub.(6-13) aryl and mixtures thereof, and n is an 
integer equal to 1-13 inclusive. 
Some of the lactams included by formula (1) are, for example, 
##STR2## 
Silicon-lactam of (A) as shown in the Statement of the Invention which can 
be used are, for example, silanes such as 
##STR3## 
where R, R.sup.1 and n are as previously defined, and R.sup.2, R.sup.3 and 
R.sup.4 are the same or different radical selected from R, R.sup.1 and 
C.sub.(1-8) alkoxy; the silicon-lactam of (A) also includes 
organosiloxanes and organosilazanes such as 
##STR4## 
and polysilanes such as, 
##STR5## 
where R, R.sup.1, R.sup.2, R.sup.3 and n are as previously defined, Q is 
selected from O and N, m has a value of 0 to 1000 inclusive and p has a 
value of 0 to 50 inclusive. 
Radicals included by R and R.sup.1 are, for example, C.sub.(1-8) alkyl such 
as methyl, ethyl, propyl, butyl, etc; halo alkyl such as chloroethyl; 
C.sub.(6-13) aryl such as phenyl, xylyl, tolyl, naphthyl; halo aryl such 
as chlorophenyl, chlorotolyl; alkaryl such as benzyl, ethylphenyl. 
Radicals included by R.sup.2, R.sup.3 and R.sup.4 include all the 
aforementioned R and R.sup.1 radicals and C.sub.(1-8) alkoxy such as 
methoxy, alkoxy, propoxy, etc. 
Some of the organosilicon material of (B) as shown in the Statement of the 
Invention can be selected from silanes and polydiorganosiloxanes and can 
be used to make the heat curable silicon containing lactam blends in situ 
when heated at temperatures up to 350.degree. C. in combination with 
lactam as previously defined. The silanes preferably have a boiling point 
of at least 25.degree. C. and are included within the formula 
EQU (R.sup.5).sub.a SiX.sub.4-a, 
where X is preferably halogen, such as chloro or carbamoto, amido, amino, 
ureido, imido, vinyloxy, aryloxy, acyloxy organosulfonate and imidazolyl, 
R.sup.5 is selected from C.sub.(1-13) monovalent hydrocarbon radicals, 
substituted C.sub.(1-13) monovalent hydrocarbon radicals, and C.sub.(1-8) 
alkoxy radicals and a has a value of 0 to 3 inclusive. Some of these 
silanes are, for example, 
allyldimethylchlorosilane; 
N,O-bis(trimethylsilyl)carbamate; 
N,O-bis(trimethylsilyl)trifluoroacetamide; 
N,N-bis(trimethylsilyl)urea; 
bromotrimethylsilane; 
1-(tert-butyldimethylsilyl)imidazole; 
tert-butyldimethylsilyltrifluoromethanesulfonate; 
tert-butyltrimethylsilylacetate; 
N-methyl-N-dimethylsilyltrifluoroacetamide. 
Among the preferred polydiorganosiloxanes which can be used in the in situ 
generation of the heat curable silicon containing lactam are compounds 
included within the formula, 
##STR6## 
where X.sup.1 is selected from R.sup.5 and X and b has a value of 0 to 
1000 inclusive. 
Some of the organosilazanes of (B) of the Statement of the Invention which 
can be used as lactam silylating agents are, for example, 
hexamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, and 
octamethylcyclotetrasilazane. 
Group I materials, or base catalysts, which can be used in the practice of 
the present invention in the heat curable blends to effect the 
polymerization of lactam preferably have a PKA of at least 13. These base 
catalysts can be, for example, alkali metals such as lithium, potassium, 
sodium, cesium, rubidium and the corresponding hydrides, hydroxides, 
carbonates, fluorides, C.sub.(1-8) alkoxides and amides such as sodium 
hydride, lithium hydride, sodium hydroxide, potassium carbonate, cesium 
fluoride, sodium amide, sodium methoxide; organo alkali compounds, for 
example, methyl, butyl and phenyl lithium. 
The term "filler" used in the description of the heating curable 
compositions of the present invention include aromatic thermoplastic 
polymers which can be in the form of a finely divided resin such as 
polyphenylene ether resins, for example, 
poly(2,6-dimethyl-1,4-phenylene)ether and preferably 
poly(2,6-dimethyl-1,4-phenylene)ether having an intrinsic viscosity of 
about 0.45 deciliters per gram (dl/g) as measured in chloroform at 
30.degree. C., aromatic polysulfones resins, polybutyleneterephthalate 
resins and polyetherimide resins. In addition to the aforementioned 
aromatic thermoplastic materials, there can be utilized finely divided 
inert fillers, including titanium dioxide, zirconium silicate, silica 
aerogel, iron oxide, diatomaceous earth, fumed silica, carbon black, 
precipitated silica, glass fibers, polyvinylchloride, ground quartz and 
calcium carbonate. The amounts of filler used can obviously be varied 
within wide limits in accordance with the intended use. There can be used 
up to 100 parts of filler, per 100 parts of the heat curable silicon 
containing lactam blends. 
In the practice of the present invention, the heat curable silicon 
containing lactam blends can be made by a dry blending procedure involving 
milling the lactam and silicon-lactam or organosilicon material along with 
the base catalyst and filler on a mill or Henchel mixer. Another procedure 
which can be used to blend the various ingredients is by converting the 
lactam or silicon-lactam or both to the liquid state to facilitate the 
intermixing of the various ingredients of the blend, such as the lactam 
ingredients, base catalyst and the filler. A third procedure which can be 
used to make the heat curable silicon-lactam blend is by forming the 
silicon-lactam in situ by heating the lactam in the presence of the base 
catalyst and organosilicon material as previously described. 
Although the order of the addition of the various ingredients is not 
critical, it is preferred to incorporate the Group I metal material before 
the temperature of the mixture achieves 140.degree. C. An effective amount 
of the Group I metal material or base catalyst in the heat curable silicon 
containing lactam blend is from 0.02 to 110 mole percent of base catalyst 
based on the moles of silicon-lactam of (A) or organosilazane or 
organosilicon material of (B). It also has been found that optimum results 
can be achieved if mixing of the various ingredients is effected under an 
inert atmosphere, such as nitrogen, particularly where the Group I 
material is sensitive to moisture or oxygen. 
In instances where a reinforcing filler or thermoplastic aromatic polymeric 
resin is added to the heat curable silicon-lactam blend to produce a 
uniform mixture, it can be pelletized by heating the blend to a 
temperature up to about 140.degree. C. to permit the ingredients to 
agglomerate together. It is preferred to store the resulting pellets in an 
inert moisture-free atmosphere at ambient temperatures if an extended 
shelf period is desired. The pellets can thereafter be heated to a 
temperature of about 150.degree. C. to 350.degree. C. to produce 
reinforced shaped parts of crosslinked polyamide in accordance with 
standard RIM or injection molding procedures.

In order that those skilled in the art will be better able to practice the 
invention, the following examples are given by way of illustration and not 
by way of limitation. All parts are by weight. 
EXAMPLE 1 
There was added 0.2 gram (0.008 mole) of sodium hydride to 10 grams (0.09 
mole) of .epsilon.-caprolactam which was in the form of a melt after being 
heated at 130.degree. C. After evolution of hydrogen gas terminated, there 
was added 0.6 gram (0.003 mole) of N-trimethylsilylcaprolactam. After the 
resulting solution was stirred for at least 10 minutes, it was heated at 
195.degree. C. The mixture polymerized for 1 minute to produce a tough 
solid. The solid was cut up into small pieces. It was found to be 
insoluble in both formic acid and meta-cresol showing it was a crosslinked 
polyamide. 
The same procedure was repeated except that 1.0 grams (0.07 mole) of cesium 
fluoride were substituted for the sodium hydride. A crosslinked, polyamide 
foam was obtained. 
EXAMPLE 2 
There are added 4 grams of polyphenylene oxide having an intrinsic 
viscosity of 0.47 dl/g in chloroform to a melt of 16.9 grams (0.15 mole) 
of .epsilon.-caprolactam and 0.6 grams (0.025 mole) of sodium hydride at a 
temperature of 130.degree. C. The resulting mixture was stirred until a 
homogeneous solution was obtained. There was then added 0.6 gram (0.003 
mole) of N-trimethylsilyl lactam and the solution was stirred for an 
additional 5 minutes at 130.degree. C. The reaction mixture was then 
heated in an oil bath to a temperature of 195.degree. C. There was 
obtained a solid blend of polyphenylene oxide and crosslinked polyamide 
after about 10 minutes of heating. 
EXAMPLE 3 
A mixture of 20 grams (0.18 mole) of caprolactam and 0.5 gram (0.02 mole) 
of sodium hydride was heated with stirring at 100.degree. C. When hydrogen 
evolution ceased, there was added 5 grams of a polyphenylene oxide having 
an intrinsic viscosity of 0.47 dl/g in chloroform at 25.degree. C. The 
mixture was stirred until a homogeneous solution was obtained. There was 
then added to the solution, 0.6 gram (0.003 mole) of 
N-trimethylsilylcaprolactam. The resulting solution was then cooled to 
room temperature to provide a solid mass. The solid mass was then diced 
into pellets. The resulting pellets are added to a mold and heated to a 
temperature of 195.degree. C. under a pressure of 100 psi. There is 
obtained a molded part in about 10 minutes. The molded part is found to be 
insoluble in meta-cresol indicating it has a crosslinked polyamide matrix. 
EXAMPLE 4 
A mixture of 5 grams (0.04 mole) of caprolactam and 5 grams (0.025 mole) of 
laurolactam was heated to a temperature of 130.degree. C. and the 
resulting melt was stirred. There was added 0.4 gram of sodium hydride and 
the mixture was stirred until hydrogen evolution ceased. There was then 
added 0.4 gram (0.002 mole) of N-trimethylsilyl lactam to the resulting 
mixture which was heated to a temperature of 195.degree. C. There was 
obtained a tough material which was found to be insoluble in meta-cresol. 
EXAMPLE 5 
There was added 0.3 grams (0.012 mole) of sodium hydride to 10 grams (0.09 
mole) of .epsilon.-caprolactam which was in the form of a melt after 
having heated at 130.degree. C. After evolution of hydrogen as terminated, 
the reaction mixture was cooled down to 80.degree. C. There was added, 
0.65 gram (0.006 mole) of chlorotrimethylsilane. The mixture was heated to 
210.degree.-220.degree. C. It polymerized in 1 minute to produce a tough 
solid. The solid was insoluble in formic acid showing it was a crosslinked 
polyamide. 
Although the above examples are directed to only a few of the very many 
variables which can be used in the practice of the present invention to 
produce heat curable silicon-lactam blends and crosslinked polyamide 
therefrom, it should be understood that the present invention is directed 
to the use of a much broader variety of lactams, silicon-lactams, Group I 
metal materials and reinforcing fillers as shown in the description 
preceding these examples.