US-12624125-B2 - Phosphorus-containing cellulose esters, methods for their preparation, their use, and flame retardants

US12624125B2US 12624125 B2US12624125 B2US 12624125B2US-12624125-B2

Abstract

The invention relates to cellulose esters, the ester groups of which are at least partially containing phosphorus and are based on unsaturated carboxylic acids and reactive phosphorus components, wherein the latter are preferably phosphorus derivatives of sugar alcohols or of tartaric acid derivatives. The invention also relates to methods for preparing novel phosphorus-containing cellulose esters and to their use as flame retardants for plastics.

Inventors

Michael Ciesielski
Elias Chalwatzis
Robin Nezami
Benedikt Sperlich

Assignees

Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.

Dates

Publication Date: 20260512
Application Date: 20200911
Priority Date: 20190911

Claims (10)

1 . A cellulose derivative of the general Formula I wherein R is the same or different on each occurrence and is selected from the group consisting of hydroxyl groups, moieties of the general formula II, and moieties of the general formula III wherein R 1 is identical or different on each occurrence and is of the formula IV: wherein R 3 , R 4 , R 5 , and n are the same or different at each occurrence, R 3 is selected from the group consisting of hydrogen or linear or branched alkyl moieties having 1 to 36 carbon atoms, and R 4 and R 5 are independently selected from the group consisting of alkyl moieties, aryl moieties, alkyl aryl moieties, arylalkyl moieties, O-alkyl moieties, O-aryl moieties, O-alkyl aryl moieties, N-alkyl moieties, N-aryl moieties, N-arylalkyl moieties, and N-alkyl aryl moieties, wherein R 4 and R 5 and the phosphorus atom can also be part of heterocyclic ring systems, which can be single or multi-membered, and wherein the heterocyclic ring system is selected from the group consisting of the following moieties: wherein R 6 is independently selected from the group consisting of alkyl moieties, aryl moieties, alkyl aryl moieties, arylalkyl moieties, O-alkyl moieties, O-aryl moieties, O-alkyl aryl moieties, N-alkyl moieties, N-aryl moieties, N-arylalkyl moieties, and N-alkyl aryl moieties; and n is 0 or an integer from 1 to 3, and R 2 is identical or different on each occurrence and is selected from the group consisting of linear or branched alkyl moieties having 1 to 36 carbon atoms and linear or branched arylalkyl moieties having 7 to 36 carbon atoms, with the proviso that in formula I, at least one R is a moiety according to formula II.
2 . The cellulose derivative according to claim 1 , wherein R 2 is identical or different on each occurrence and is selected from the group consisting of linear or branched alkyl moieties having 1 to 12 carbon atoms and linear or branched arylalkyl moieties having 7 to 14 carbon atoms.
3 . The cellulose derivative according to claim 1 , wherein, based on all moieties R, the molar proportion of the moieties according to formula II is 40 to 90 mol %, of the moieties according to formula III, is 10 to 90 mol %, and/or the hydroxyl groups is a maximum of 50 mol %.
4 . A method of imparting flame retardancy to a plastic material comprising incorporating into the plastic material an effective amount of a cellulose derivative of general formula I according to claim 1 .
5 . The method of claim 4 , wherein the plastic material is a thermoplastic material.
6 . The method of claim 4 , wherein the plastic material is selected from the group consisting of a polyester, a polyamide, a polyolefin, a polycarbonate, PMMA, polystyrene, styrene block polymer, a cellulose ester, a polyurethane, and an epoxy resin, each of which is unfilled, filled, or reinforced.
7 . A flame retardant composition comprising at least one cellulose derivative of the general formula I according to claim 1 and at least one further flame retardant differing from the cellulose derivative of the general formula I.
8 . The flame retardant composition according to claim 7 , wherein the at least one further flame retardant differing from the cellulose derivative of the general formula I is selected from the group consisting of metal hydroxides, melamine derivatives, nitrogen bases, phosphates, phosphonates, phosphinates, pyrophosphates, polyphosphates, siloxanes, and pentaerythritol.
9 . The flame retardant composition according to claim 7 , wherein the at least one further flame retardant differing from the cellulose derivative of the general formula I is selected from the group consisting of magnesium hydroxide, aluminum hydroxide, boehmite, melamine polyphosphate, ammonium polyphosphate, melamine cyanurate, zinc pyrophosphate, piperazine pyrophosphate, piperazine polyphosphate, and 1,3,5-tris(2-hydroxyethyl)isocyanurate.
10 . A plastic composition comprising of at least one plastic material and at least one cellulose derivative of the general formula I according to claim 1 , wherein the at least one cellulose derivative of the general formula I is added in a flame retardancy effective amount.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This patent application is the U.S. national phase of International Application No. PCT/EP2020/075448, filed on Sep. 11, 2020, which claims the benefit of German Patent Application No. 10 2019 213 793.8, filed Sep. 11, 2019, the disclosures of which are incorporated herein by reference in their entireties for all purposes. The invention relates to cellulose esters, the ester groups of which contain at least some phosphorus and are based on unsaturated carboxylic acids and reactive phosphorus components, the latter preferably being phosphorus derivatives of sugar alcohols or tartaric acid derivatives. The invention also relates to methods for producing the novel phosphorus-containing cellulose esters and their use as flame retardants for plastics. Easy flammability or combustibility is a disadvantage of most plastic materials, which disadvantage must be overcome or mitigated for numerous applications with the aid of flame retardants. In addition to mineral additives and polyphosphates, which usually have to be added in considerable quantities and in many cases worsen the material properties, and special flame retardant additives having only limited areas of use, halogen-containing flame retardants are of great importance since they are efficient, inexpensive and effect material parameters less. However, the latter can give rise to health risks, in particular in the event of a fire due to the release of toxic gases, and cause environmental problems, not least when disposing of the plastics that they contain. This applies in particular to combinations of halogen-containing flame retardants having the synergist antimony(III) oxide, which are used on a large scale in engineering plastics and polyolefins. Flame retardants which do not have these disadvantages and can be produced from renewable raw materials are desirable. Special organophosphorus compounds, which are less of an ecological and health concern, have become important as an alternative to halogen-containing flame retardants. Both the exclusive use of such phosphates, phosphinates and phosphonates as flame retardants is known, as is their use as a component of flame retardant mixtures or synergistic flame retardant systems, for example, in combinations with 1,3,5-triazine compounds or polyphosphates. When used as flame retardants, macromolecular organophosphorus compounds have the advantage that, compared to corresponding low molecular weight phosphorus compounds, they produce less plasticizer effect, which in many cases is undesirable because of the deterioration in material properties, and show hardly any tendency to migrate out of the material. The use of macromolecular phosphorus compounds as flame retardants for plastics is already known. WO 2009/109347 A1 describes a linear phosphorus-containing polyester based on itaconic acid and ethylene glycol and is obtained by means of phospha-Michael addition of DOPO to itaconic acid or itaconic acid derivatives and subsequent polycondensation with ethylene glycol. Said polyester softens or melts even at relatively low temperatures, which is disadvantageous when incorporated into plastics. DE 10 2013 101 487 A1 describes phosphorus-containing thermosets. Said thermosets have a basic polyacrylate structure and are also obtained in a two-stage process. First, a suitable phosphorus component, for example, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), is added to polyfunctional acrylates by means of phospha-Michael addition, wherein the stoichiometric ratio is chosen so that on average, more than one free acrylate group remains per molecule. The remaining acrylate functionalities are then converted by means of radical polymerization, leading to crosslinking and the formation of the thermoset. These macromolecular flame retardants are only suitable for special areas of application. The highest possible proportion of bio-based structural components is increasingly desired for phosphorus-containing flame retardants, in addition to macromolecular properties. One starting material of the phosphorus-containing polyester described in WO 2009/109347 A1, itaconic acid, is bio-based, but the other two are not, so that the proportion of renewable raw materials is relatively low. Furthermore, phosphorus-containing flame retardants based on cellulose, starch, lignin, oligomeric sugars, castor oil, etc. were synthesized and tested. In addition, flame retardants were produced in which some of the starting materials, such as pentaerythritol, special phenols or other starting materials, were obtained from renewable raw materials. While the former flame retardants have disadvantages compared to conventional, non-bio-based flame retardants with regard to their thermal stability, material compatibility, etc. and are therefore hardly suitable for high-performance polymers, in the latter, the bio-based proportion is usually only moderate, in particular when the synthetic chemical