Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Patent
1998-05-22
2000-05-16
Green, Anthony
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
106724, 106806, 106823, 524 4, 524 5, 524588, 526240, 526279, C08F22220, C08F29006, C04B 2426
Patent
active
060631848
DESCRIPTION:
BRIEF SUMMARY
This invention relates to styrene-maleic anhydride copolymers and to their use as additives in cementitious compositions.
Styrene-maleic anhydride copolymers ("SMA") are common items of commerce and are used in a wide variety of applications. In recent years, modified SMAs in which the maleic anhydride ring has been partially esterified with poly(alkylene glycol) have been used as admixtures in cementitious compositions such as concretes and mortars. They are useful as superplasticisers, that is, admixtures which allow the cementitious composition to remain flowable at a considerably reduced water content, thus resulting in good working properties and better quality final hardened product. An especially effective SMA is described in French Published Application No. 2 671 090.
It has now been found that it is possible to prepare an SMA which provides a surprising degree of even higher performance. The invention therefore provides a random styrene-maleic anhydride copolymer in free acid or salt form, wherein the copolymer consists of the following types and numbers of monomer units: ##STR2## in which: M is selected from hydrogen, a cation and a residue of a hydrophobic polyalkylene glycol or polysiloxane; (weight-average) 900-2000;
In a preferred embodiment, the molecular weight of R is from 900-1500 and the values of x and y are respectively 0.55-0.75 and 0.25-0.45.
It will be clear to the man skilled in the art that all numbers given above are average values. It will also be clear that in such a polymer, M may be one, all or any combination of the four possible moieties hereinabove described.
The SMAs according to this invention preferably have an average molecular weight (weight-average) from 10,000 to 50,000, more preferably from 10,000 to 25,000 and preferably have an even distribution of styrene and maleic acid half ester units, i.e. the ratio of styrene units to maleic anhydride units is about 1:1. The skilled person will understand that some deviation from this ratio is permissible, but it is preferred that the ratio remain within the range S:MA of from 1:0.8-1:1.2. Most preferred copolymers have an average molecular weight of about 13,000. When salt forms are desired (i.e., when M is a cation), they may be any suitable salt forms, and for example, alkali and alkaline earth metal salts, ammonium and hydroxyalkyl ammonium salts, amino salts, and so on.
The residue of methoxypoly(ethylene glycol) ether has the formula (weight-average) is given. Preferably the molecular weight is from 900-1500, more prefereably from 1000-1300; it has been found that, in this relatively narrow range, the best properties are given.
When M is not hydrogen or a cation, it is the residue of a copolymer consisting of units derived from ethylene oxide and propylene oxide, the residue of a polypropylene glycol having from 10 to 200 units derived from propylene oxide or the residue of a polysiloxane consisting of di-C.sub.1-4 alkylsiloxane units. The ethyleneoxide/propylene oxide copolymers may be represented by formula I ##STR3## in which R.sub.2 is hydrogen or C.sub.1-6 alkyl, and p, q and r are numbers from 0 to 100 with the provisos that at least one of p, q, and r is at least 1, and that q>p+r. Preferred polysiloxanes correspond to formula II ##STR4## in which q has the same significance as previously mentioned.
Typical examples of suitable, commercially-available hydrophobic polyalkylene glycols include:
______________________________________ "Pluronic" PE 6100 (BASF)
"Pluronic" PE 3100 (BASF)
SYNPERONIC PE L-61 (ICI)
DOWFAX 20 A 64 (DOW)
DOWFAX 20 A 612 (DOW)
SYNALOX 50-50 B (DOW)
SYNALOX 100-150 D (DOW)
SYNALOX 100-D95 (DOW)
CC-118 (Nippon Oil & Fats)
CD-115 (MBT)
______________________________________
Typical examples of suitable, commercially-available polysiloxanes include:
______________________________________ VP 1610 (Wacker)
SLM 50400/61 (Wacker)
SLM 50400/62 (Wacker)
SLM 50480/6 (Wacker)
______________________________________
It is not practically possible to
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Copy of GB Patent Office Search Report for GB Application No. 9607570.0 dated Aug. 12, 1996.
Leikauf Bernhard
Oppliger Max
Valenti Salvatore
Green Anthony
MBT Holding AG
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