Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-03-05
2002-05-07
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000, C264S165000, C264S176100, C428S064200
Reexamination Certificate
active
06384178
ABSTRACT:
The present invention relates to a process for the preparation of polycarbonate diols (PCD) with a high molecular weight comprising two subsequent reaction steps wherein in the first step PCD with a molecular weight ranging from 500 to 2000, is synthesized and in the second step the molecular weight of the PCD is increased to the desired value.
Polycarbonate diols are a group of oligomeric polyols which are used in the synthesis of prepolymers with an isocyanate functionality useful in the production of thermoelastomeric polyurethanes which are used for the preparation of paints, adhesives and seals.
In particular, PCD with a high molecular weight, i.e. higher than 2000, can be used in formulations for the production of polyurethane adhesives of the reactive hot-melt type (HMR moisture curing), as well as in polymerization processes in emulsion, as for example in the production of synthetic leather, where they increase the coagulation rate of the polyurethane obtained with a consequent improvement in the tear strength.
The preparation of polycarbonate diols by the carbonylation of an aliphatic glycol with a carbonylating agent, optionally in the presence of suitable catalysts, is known in the art.
For example patents U.S. Pat. Nos. 2,789,964 and 3,000,849 describe the use of alkyl carbonates as carbonylating agents. Operating according to these processes, however, it is difficult to obtain PCD with a correct hydroxyl functionality. The problem is particularly significant in the case of the synthesis of PCD with a high molecular weight, for example higher than 2000 (referring to the number average).
A second method is based on the use of aromatic carbonates (U.S. Pat. No. 3,544,524) whose considerable reactivity allows the transesterification reaction to be carried out without catalysts. This process produces PCD with a high molecular weight and with a correct hydroxyl functionality.
The high molecular mass of the aromatic carbonate used as carbonylating agent, however, reduces the space yield of reactors and implies the production of a stream of phenol distillate whose entity makes the process of little economic interest.
Another method comprises the use of phosgene (U.S. Pat. No. 4,533,729), a toxic chemical reagent which can be synthesized and used only in appropriate industrial areas. The high acidity, moreover, jeopardizes the quality of the PCD obtained, necessitating the use of acid receptors to control it.
A simple and economic process has now been found for the preparation of polycarbonate diols with a high molecular weight and with a correct hydroxyl functionality which overcomes the drawbacks of the known art described above.
In accordance with this, an objective of the present invention relates to a process for the production of polycarbonate diols with a molecular weight higher than 2000 having general formula (I)
HO—R′—[OCOOR′]
n
—OH (I)
wherein: n is an integer or decimal ranging from 5 to 40 and R′ is a bivalent alkylene radical deriving from a diol by the loss of two hydroxyls, said process comprising:
(a) a first reaction step wherein a polycarbonate diol is prepared with a molecular weight ranging from 500 to 2000, having general formula (II)
HO—R′—[OCOOR′]
n′
—OH (II)
wherein n′ is an integer or decimal<n and ranging from 2 to 20 and R′ has the meaning defined above, by reacting an alkyl carbonate having formula (III)
RO—CO—OR (III)
wherein R is a C
1
-C
4
alkyl radical with a linear or branched chain, with an aliphatic diol having formula (IV)
HO—R′—OH (IV)
wherein R′ has the meaning defined above, in the presence of a transesterification catalyst, eliminating the alcohol from the reaction mixture; and
(b) a second step wherein the mixture containing the compound having formula (II) obtained in the first step is reacted with an aryl carbonate ArO—CO—OAr (V).
Step a
In this step the diol (IV) and the carbonate (III) are reacted, in the presence of a transesterification catalyst, according to the following scheme (i)
n′RO—CO—OR+(n′+1) HO—R′—OH→HO—R′—[OCOOR′]
n′
—OH+2n′R—OH (i)
wherein R, R′ and n′ have the meaning defined above.
The diol (IV) and the carbonate (III) are used in a molar ratio ranging from 2/1 to 1.05/1, preferably from 1.2/1 to 1.07/1.
In the compounds have formula (I), R′ is selected from:
1. linear or branched alkylene radicals or cycloalkylene radicals containing from 3 to 14 carbon atoms; said radicals may optionally have one or more substituents which do not interfere with the transesterification reaction.
2. bivalent radicals deriving from polyether dials having formula (V):
HO—[(CHR)
d
—O]
x
—H (V)
wherein: d is a number which can vary from 2 to 4, x can vary from 1 to 25 and R can be H and/or CH
3
.
3. bivalent radicals deriving from polyester dials having formula (VI)
HO—[(CHR″)
f
—COO—(CH
2
)
g
—O]
y
—H (VI)
deriving from the condensation of a lactone with a linear aliphatic diol and wherein f is a number ranging from 3 to 6, g is a number ranging from 3 to 14, y is a number ranging from 1 to 10 and R″ can be H and/or CH
3
.
4. a mixture of two or more bivalent radicals selected from those listed under points 1-3.
Examples of R′ radicals are those deriving from the following diols: 1,6-hexanediol (HD), 1,3-propanediol, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, 1,5-pentanediol, 1,4-bis(hydroxymethyl-cyclohexane), diethyleneglycol (DEG), triethylene glycol (TEG), polyethyleneglycol (PEG/Mn 200-400), dipropylene glycol (DPG), poly-propylene glycol (PPG/Mn 200-400), polytetramethyleneglycol (PTMEG/Mn 250), the diol deriving from the condensation of caprolactone with 1,6-hexanediol. 1,6-hexanediol is preferred.
Examples of R radicals are those deriving from the following carbonates: dimethyl carbonate (DMDC), diethyl carbonate (DEC), dipropyl carbonate (dnpc), diisopropyl carbonate (dipc), dibutylcarbonate (dnbc), diisobutylcarbonate (dibc). Dimethyl carbonate is preferred.
Transesterification catalysts suitable for the purpose generally consist of organometallic compounds based on metals of group IV B in the tetravalent state such as titanium, zirconium and tin. Compounds of titanium and tin are preferred.
Examples of titanium compounds are tetra alcoholates of ethyl, propyl, isopropyl, butyl, iso-octyl and phenyl.
Examples of tin compounds are dibutyl tin di-laurate, dibutyl tin octoate and tin oxalate.
The quantity of catalyst used, referring to the metal which forms the active center, generally ranges from 1 to 1000 mg/kg of diol, preferably from 5 to 100 mg/kg.
The reaction is carried out at a temperature ranging from 150 to 200° C. and under boiling conditions at the operating pressure, the alcohol R—OH co-produced by the transesterification being removed as it is formed.
Temperatures lower than the first limit indicated can be used but are not advantageous as the reaction rate is too low, whereas temperatures higher than the second limit favour secondary reactions such as the formation of ether bridges by the decarboxylation of the carbonate bridges in the polymeric chain, or, in relation to the structure of the monomeric diol, the elimination of cyclic ethers deriving from the same monomeric diol.
Temperatures ranging from 180 to 195° C. are preferably used.
The pressure at which the reaction is carried out depends on the vapor pressure of the reaction mixture at the temperature indicated for the reaction and, in any case, is such as to allow the removal by boiling of the alcohol co-produced by the transesterification.
If DMC is used, the methanol is removed in the form of an azeotropic mixture with the carbonate itself. In this case, an additional quantity of DMC equal to that removed by distillation with the methanol, is added to the quantity of DMC put into the reaction with the purpose of reacting with the diol.
The pressure adopted
Mizia Franco
Rivetti Franco
Boykin Terressa M.
Enichem S.p.A.
LandOfFree
Process for the preparation of polycarbonate diols with a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the preparation of polycarbonate diols with a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of polycarbonate diols with a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2896855