More specifically, the present invention relates to a granular form of a mixture of a nickel-quencher and a 2-hydroxy-4-alkyloxybenzophenone, a process for its preparation and its use as a light stabilizer for agricultural films based on polyolefins or olefinic copolymers.

The present invention also relates to agricultural films based on polyolefins or olefinic copolymers stabilized with the above granular form and greenhouses covered with these films.

Nickel-quenchers are at present sold in fine powder form and their use causes problems of environ- mental pollution, health and the safety of the opera- tors in the feeding and handling phase.

A benzophenone is also generally used in the

stabilization of agricultural films, together with nickel-quenchers.

Conventional methods for obtaining a physical form of nickel-quencher with a low powder content (for example, compaction of the powders under pressure) tested on both the nickel-quencher alone, and on mixtures of nickel-quenchers and benzophenones, have proved to be inapplicable or have not given satisfacto- ry results.

The Applicant has now found a granular form of a mixture of a nickel-quencher and a benzophenone capable of overcoming the drawbacks of the known art.

The present invention therefore relates to a granular form of a mixture comprising: (a) a nickel-quencher corresponding to [2,2'-thio- bis (4-t-octyl-phenolate)-n-butylamineNickel (II)] having formula (I): (b) a 2-hydroxy-4-alkyloxybenzophenone corresponding to 2-hydroxy-4-n-octyloxybenzophenone having formula (II):

characterized in that it has two diffraction lines at angles 28 = 17.593 and 28 = 22.023 in the X-Ray dif- fraction spectrum from powders.

The X-Ray diffraction spectrum from powders is carried out using Cru-ka radiation (A = 1.54178).

In the granular form of the present invention, the nickel-quencher (a) having formula (I) and the benzo- phenone (b) having formula (II), are used in a ratio ranging from 0.4 to 3, preferably in a ratio ranging from 1 to 2.

The nickel-quencher (a) having formula (I) is known under the following trade-names: Cyasorb W 1084 of Cytec, or Chimassorb N-705 of Ciba.

The benzophenone (b) having formula (II) is known under the following trade-names: Lowilite 22 of Great Lakes, Chimassorb 81 of Ciba, or Cyasorb UV 531 of Cytec.

The granular form of the present invention can be

obtained according to the following process.

A process for the preparation of the granular form of the present invention comprises: (1) dissolving, under stirring, the nickel-quencher (a) having formula (I) in the benzophenone (b) having formula (II) which has been previously melted at 50°C; (2) cooling the solution obtained as described under point (1).

Step (1) of the above process is carried out at a different temperature depending on the ratio between the nickel-quencher (a) having formula (I) and the benzophenone (b) having formula (II), used: step (1) of the present invention is generally carried out at a temperature ranging from 50°C to 150°C, preferably between 50°C and 120°C.

The cooling according to step (2) of the above process, suitable for causing the solidification of the solution obtained as described in point (1), can be obtained with any of the methods known in the art.

The preferred methods consist in: -pouring the solution onto a cold metal plate maintained, for example, at a temperature equal to or less than room temperature: in this case the solid obtained must be granulated so as to obtain

granules having the desired dimensions; -dripping the solution onto a cold metal plate maintained, for example, at a temperature equal to or less than room temperature: in this case drops are obtained already having the desired dimen- sions.

The nickel-quencher (a) and benzophenone (b) powders and the granules obtained as described above, are subjected to X-Ray diffraction and the spectra obtained are indicated in the following figures: -Fig. 1: X-Ray diffraction spectrum from powders of the nickel-quencher (a) in powder form; -Fig. 2: X-Ray diffraction spectrum from powders of benzophenone (b) in powder form; -Fig. 3: X-Ray diffraction spectrum from powders of the physical mixture of nickel-quencher (a) and benzophenone (b) powders; -Fig. 4: X-Ray diffraction spectrum from powders of the granules obtained, as described above, from the mixture of nickel-quencher (a) and benzophe- none (b) powders.

As can be observe, Fig. 4 shows two diffraction lines at angles 28-17.593 and 28 = 22.023 in the X- Ray diffraction spectrum from powders which are not present in the X-Ray diffraction spectrum from powders

of the nickel-quencher (a) and benzophenone (b) alone (Fig. 1 and 2) and their physical mixture (Fig. 3).

The granular form of the present invention has a melting range between 47°C and 50°C, measured by Buchi Instrument (tube of 1 mm of diameter). As an additive having a low melting point generally has a shorter homogenization time in the polymer to which it is added, it is evident that, in addition to the avantage of overcoming the drawbacks of the known art described above, the granular form of the present invention also guarantees a more rapid homogenization of the additives inside the polymer. In addition, as the process for the preparation of the granular form of the present inven- tion comprises, in step (a), a phase in which both compounds (a) and (b) are in the liquid state, there is also a perfectly homogeneous distribution of the two additives therein (for example, mechanical mixing of the two powders does not produce a mixture having the same degree of homogeneity).

As already mentioned above, the granular form of the present invention can be used as a light stabilizer for agricultural films based on polyolefins and olefin- ic copolymers.

Polyolefins and olefinic copolymers which can be used for the purpose are:

(1) polymers of mono-olefins and diolefins such as, for example, polypropylene, polyisobutylene, polybut-1-ene, poly-4-methylpent-1-ene, polyiso- prene or polybutadiene; as well as polymers of cyclo-olefins such as, for example, cyclopentene or norbornene; polyethylene (which can be option- ally cross-linked) such as, for example, high density polyethylene (HDPE), low density polyeth- ylene (LDPE), linear low density polyethylene (LLDPE), branched low density polyethylene (BLDPE).

Polyolefins such as, for example the mono-olefins mentioned in the above paragraph, preferably polyethyl- ene and polypropylene, can be prepared with various methods known in literature, preferably using the following methods: (a) radicalic polymerization (generally carried out at a high pressure and high temperature); (b) catalytic polymerization using a catalyst which normally contains one or more metals of groups IVb, Vb, VIb or VIII of the Periodic Table. These metals generally have one or more ligands such as, for example, oxides, halides, alcoholates, ethers, amines, alkyls, alkenyls and/or aryls which can be 7-or a-co-ordinated. These metal complexes can be

in free form or supported on substrates such as, for example activated magnesium chloride, titani- um (III) chloride, alumina or silicon oxide. These catalysts can be soluble or insoluble in the poly- merization medium. The catalysts can be used alone or in the presence of other activators such as, for example, metal alkyls, metal hydrides, halides of metal alkyls, oxides of metal alkyls or metal alkyloxanes, these metals being elements belonging to groups Ia, IIa and/or IIIa of the Periodic Table. The activators can be conveniently modified with other ester, ether, amine or silyl-ether groups. These catalytic systems are usually called Phillips, Standard Oil Indiana, Ziegler (-Natta), TNZ (Du-Pont), metallocene or"single site cata- lyst" (SSC).

(2) Mixtures of the polymers described under point (1) such as, for example, mixtures of polypropylene with polyisobutylene; mixtures of polypropylene with polyethylene (for example, PP/HDPE, PP/LDPE); mixtures of different types of polyethylene (for example, LDPE/HDPE).

(3) Copolymers of mono-olefins and diolefins with each other or with other vinyl monomers such as, for example, ethylene-propylene copolymers, linear low

density polyethylene (LLDPE) and its mixtures with low density polyethylene (LDPE), propylene/but ene copolymers, propylene/isobutylene copolymers, ethylene/but-l-ene copolymers, ethylene/hexene copolymers, ethylene/methylpentene copolymers, ethylene/heptene copolymers, ethylene/octene copolymers, propylene/butadiene copolymers, isobutylene/isoprene copolymers, ethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylate copolymers, ethylene/vinyl acetate copolymers and their copolymers with carbon monoxide or ethyl- ene/acrylic acid copolymers and their salts (ionomers) as well as terpolymers of ethylene with polypropylene and a diene such as, for example, hexadiene, dicyclopentadiene or ethylidene-norbor- nene; and mixtures of these copolymers with each other or with the polymers cited in paragraph (1) such as, for example, polypropylene/ethylene- propylene copolymers, LDPE/ethylene-vinylacetate (EVA) copolymers, LDPE/ethylene-acrylic acid (EAA) copolymers, LLDPE/EVA, LLDPE/EAA, and alternating or random polyalkylene/carbon monoxide copolymers and their mixtures with other polymers such as, for example, polyamides.

Preferred for the purpose are polymers of mono-

olefins, preferably a-mono-olefins such as, for exam- ple, polypropylene, polyisobutylene, polybut-1-ene, poly-4-methylpent-1-ene, as well as polymers of cyclo- olefins, polyethylene (which can be optionally cross- linked) such as, for example, high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), branched low density polyethylene (BLDPE) and copolymers of these monomers with vinyl acetate. Even more preferred are polyethyl- ene, ethylene/propylene copolymer, ethylene/vinyl acetate copolymer and polypropylene, in particular polyethylene, preferably low density polyethylene (LDPE).

A further object of the present invention relates to agricultural films based on polyolefins or olefinic copolymers containing an effective quantity of the granular form described above.

The granular form of the present invention can be used as such or combined with other stabilizers, in the above polymeric agricultural films.

The granular form of the present invention is generally used in a quantity ranging from about 0.1% to about 2% with respect to the weight of the films to be stabilized, preferably between about 0.2% and about 1%.

The granular form of the present invention,

optionally in the presence of other additives, can be easily incorporated into the polymers to be stabilized using the conventional techniques.

The resulting polymeric compositions can be transformed into films operating according to the conventional techniques.

The above films based on polyolefins or olefinic copolymers, can contain metal oxides or hydroxides such as, for example, oxides of zinc, aluminum, calcium or magnesium, or hydroxides of zinc, aluminum or calcium, <BR> <BR> <BR> <BR> <BR> <BR> preferably zinc oxide (ZnO), zinc hydroxide [Zn (OH) 23,<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> aluminum ortho-or meta-hydroxide [Al (OH) 3], aluminum a- or y-oxide, magnesium oxide (MgO). Zinc oxides or hydroxides are preferred, zinc oxide is even more preferred.

The above metal oxides or hydroxides are generally added in a quantity ranging from 0.005% to 3% by weight with respect to the weight of the films to be stabi- lized, preferably between 0.005% and 1% by weight, even more preferably between 0.025% and 0.5% by weight.

In many cases, the above films contain a salt of a Ci-c 30 carboxylic acid, preferably a salt of a C8-C22 carboxylic acid, even more preferably a salt of a C8-C18 carboxylic acid.

Preferred films are those which contain one or

more components selected from salts of earth-alkaline metals, zinc salts and aluminum salts of a Cl-C30 carboxylic acid, hydrotalcites, and sterically hindered amines.

Films based on polyolefins or olefinic copolymers containing salts of a Cl-c30 carboxylic acid are of greatest interest for the purpose. Metal carboxylates which can be optionally added are, mainly, salts of Al, Ba, Ca, Mg, Sr or Zn. Salts of A1, Ca, Mg or Zn, especially of C 12-c18 carboxylic acids, are preferred.

Calcium salts such as, for example, calcium stearate, are even more preferred.

The metal carboxylates are used in a quantity ranging from 0.05% to 2% by weight with respect to the weight of the films to be stabilized, preferably between 0.1% and 1% by weight.

The sterically hindered amines are added in a quantity ranging from about 0.01% to 5% by weight with respect to the weight of the films to be stabilized, preferably between 0.025% and 2% by weight, even more preferably between 0.05% and 1% by weight.

The films described above may advantageously contain a hydrotalcite. Hydrotalcites which can be used for the purpose are selected from those having the following general formula (III):

M2+1-x#M3+x#(OH)2#(An-)x/n#pH2O(III) wherein: -M2+ is Mg, Ca, Sr, Ba, Zn, Pb, Sn and/or Ni; -mois Al, B or Bi; -An-is an anion of the valency n; -n is a number between 1 and 4 extremes included; -x is a number between 0 and 0.5 extremes included; -p is a number between 0 and 2 extremes included; <BR> <BR> <BR> <BR> <BR> -A is OH-, Cl-, Br-, I-, C104', HC03', CH3COO-, C6H5COO- (COO)22-,(CHOHCOO)22-,(CHOH)4CH2OHCOO-,CO32-,SO42-, C2H4 (COO) ',(CHCOO)',CHCHOHCOO',SiO',SiO', Fe (CN) ', Fe (CN) 64 , BO33 , PO33 HPO'.

Preferred hydrotalcites having general formula (III) are those wherein M2+ is Ca2+, Mg2+ or a mixture of Mg2+ and Zn2+, An- is CO32-, BO33- or PO33-, x is a number between 0 and 0.5 extremes included and p is a number between 0 and 2 extremes included.

Other hydrotalcites which can be advantageously used are those having general formula (IIIa): Mx2+A12 (OH) (A"-),.pH,0(Ilia) wherein: M2+ is Mg or Zn, preferably Mg; -A"'is an anion selected from CO32-, (COO) 2, OH'and SZ~, wherein n is the valency of the anion.

-p is a positive number, preferably between 0 and

5 extremes included, for example between 0.5 and 5 extremes included; -x is a positive number preferably between 2 and 6 extremes included; -z is a positive number less than 2.

Preferred hydrotalcites having general formula (IIIa) are those represented by the following formulae <BR> <BR> <BR> <BR> <BR> (IIIb)- (IIIh) :<BR> <BR> <BR> <BR> <BR> <BR> ;Al2O3#5MgO#CO2#12H2O(IIb) <BR> <BR> <BR> <BR> <BR> <BR> <BR> (IIIc);Mg4.5Al2(OH)13#CO3#3.5H2O 4MgO A1203 CO2 9H2O (IIId); 4MgO Al203 CO2 6H2O (IIIe); <BR> <BR> <BR> <BR> (IIIf);ZnO#3MgO#Al2O3#CO2#8-9H2O <BR> <BR> <BR> <BR> <BR> <BR> ;ZnO#3MgO#Al2O3#CO2#5-6H2O(IIIg) <BR> <BR> <BR> <BR> <BR> <BR> <BR> (IIIh).Mg4.5Al2(OH)13#CO3 Hydrotalcites can be advantageously used in a quantity ranging from 0.01% to 5% by weight with respect to the weight of the films to be stabilized, preferably between 0.2% and 3% by weight.

Useful sterically hindered amines which can be added to the films described above, can be single compounds or mixtures of compounds. In the case of mixtures, the quantities indicated above refer to the total quantity of sterically hindered amines used.

Sterically hindered amines refer to compounds containing one or more trivalent groups having general formula (IV): wherein G is hydrogen or methyl and not more than one of the free valencies in the above general formula (IV) is saturated with a hydrogen and 2 or 3 of the free valencies represent bonds with carbon atoms or hetero- atoms.

Examples of the above sterically hindered amines are described, for example, in U. S. patents 4,086,204, 4,108,829,4,263,434,4,233,412,4,288,593,4,315,859, 4,321,374,4,331,586,4,413,093,4,435,555,4,477,615, 4,335,242,4,376,836,4,433,145,4,459,395,4,477,615, 4,533,688,4,540,728,4,547,548 and 4,740,544; in European patent applications EP 22,080, EP 29,522, EP 24,338, EP 42,554, EP 44,499, EP 70,386, EP 72,009, EP 75,849, EP 82,244, EP 94,048, EP 107,615, EP 402,889 and EP 357,223; and in German patent application DE 3,530,666; the texts of the above documents should be considered as forming an integrant part of the present description.

In many cases, the sterically hindered amines are

cyclic, in particular they are compounds selected from polyalkyliperidine derivatives containing at least one group having general formula (V) :

wherein G is hydrogen or methyl, and G1 and G2 are hydrogen, methyl or, together, they are a substi- tuent =0; the polyalkylpiperidine groups having general formula (V) are generally substituted in position 4 by one or two polar substituents or by a polar ring having a spiro structure.

Of particular importance are cyclic stearically hindered amines containing at least one group having general formula (V) where G is hydrogen anf G, and G2 are hydrogen or, together, are substituent =0.

In particular, derivatives of 2,2,6,6-tetramethyl- piperidine are advantageously used.

Of particular importance is the use of compounds belonging to the group of polyalkylpiperidine carrying at least one group having general formula (V) in the molecule, selected from those listed below under points (a)- (i).

(a) Compounds having general formula (VI):

Wherein n is a number between 1 and 4 extremes included; G and G1 are, each independently, hydro- gen or methyl; Gll is hydrogen, a Cl-Ci8 alkyl group, a C3-C8 alkenyl group, a C3-Cs alkinyl group, a Cl7-Cl2 aralalkyl group, a Cl-Ce alkanoyl group, a C3-C5 alkenoyl group, a glycidyl group, a -CH2CH (OH)-Z group wherein Z is hydrogen, methyl, or phenyl, G11 preferably being hydrogen, a C1-C4 alkyi group, an allyl, a benzyl, an acetyl or an acryloyl; Glz, when n is 1, is hydrogen, a Cl-Cl8 alkyl group which can be interrupted by one or more oxygen atoms, a cyanoethyl group, a benzyl, a glycidyl group, a monovalent radical of a carboxylic acid, of a carbamic acid or of an acid containing phosphorous, aliphatic, cycloaliphatic or araliphatic, unsatured or aromatic, or a monovalent silyl radical, preferably a radical of an aliphatic carboxylic acid having from 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid

having from 7 to 15 carbon atoms, of an a, S-un- saturated carboxylic acid having from 3 to 5 carbon atoms, of an aromatic carboxylic acid having from 7 to 15 carbon atoms, said carboxylic acids optionally substituted in the aliphatic, cycloaliphatic or aromatic part with 1-3-COOzl2 groups wherein Z12 is hydrogen, a Cl-c2, alkyl group, a C3-C12 alkenyl group, a C5-C7 cycloalkyl group, a phenyl or a benzyl; G12, when n is 2, is a C2-C12 alkylene group, a C4-cl2 alkenylenic group, a xylylene group, a divalent radical of a dicarbo- xylic acid, of a dicarbamic acid or of an acid containing phosphorous, aliphatic, cycloaliphatic, araliphatic or aromatic, or a divalent silyl rad- ical, preferably a radical of an aliphatic dica- rboxylic acid having from 2 to 36 carbon atoms, of a cycloaliphatic or aromatic dicarboxylic acid having from 8 to 14 carbon atoms, of an aliphatic, cycloaliphatic or aromatic dicarbamic acid having from 8 to 14 carbon atoms, said dicarboxylic acids optionally substituted in the aliphatic, cycloali- phatic or aromatic part, with 1 or 2-COOZl2 groups wherein Z12 has the same meanings described above; G12, when n is 3, is a trivalent radical of an aliphatic, cycloaliphatic or aromatic tricarboxyl-

ic acid, optionally substituted in the aliphatic, cycloaliphatic or aromatic part, with a-COOZlz group wherein Z12 has the same meanings described above, or of an aromatic tricarbamic acid or of an acid containing phosphorous, or it is a trivalent silyl radical; G12, when n is 4, is a tetravalent radical of an aliphatic, cycloaliphatic or aromat- ic tetracarboxylic acid.

Radicals of tetracarboxylic acids comprise, in any case, radicals having the formula (-CO) nR wherein n has the same meaning defined above and R can be easily deduced from the definition described above.

Examples of Cl-cl2 alkyl groups are: methyl, ethyl, n-propyl, n-butyl, sec-butyl, t-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, etc.

Examples of G11 and G12 substituents, when they are a Cl-Cl8 alkyl group, are, in addition to the groups described above: n-tridecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, etc.

Examples of the substituent Girl, when it is a C3-C8 alkenyl group, are: 1-propenyl, allyl, methallyl, 2-bu- tenyl, 2-pentenyl, 2-hexenyl, 2-octenyl, 4-t-butyl-2- butenyl, etc.

When the substituent Girl ils a C3-C8 alkinyl group,

it is preferably propargyl.

When the substituent Girl ils a C7-C12 aralalkyl group, it is in particular phenethyl, preferably benzyl.

Examples of the substituent Girl, when it is a C1-C8 alkanoyl group, are: formyl, propionyl, butyryl, octanoyl, preferably acetyl and, when it is a C3-C5 alkenoyl group, preferably acryloyl.

Examplesof the substituent G12, when it is a monovalent radical of a carboxylic acid, are radicals of the following acids: acetic, caproic, stearic, acrylic, methacrylic, benzoic, 9- (3,5-di-tert-butyl-4- hydroxyphenyl) propionic, etc.

Examples of the substituent G12, when it is a monovalent silyl radical, are: a radical having the general formula -(CjH2j) -Si (Z') zZ''wherein j is an integer between 2 and 5 extremes included, and Z'and Z''are, each independently, a Ci-c4 alkyl group or a aroup.C1-C4alkoxyl Examples of the substituent G12, when it is a divalent radical of a dicarboxylic acid, are radicals of the following acids: malonic, succinic, glutaric, adipic, suberic, sebacic, maleic, itaconic, phthalic, dibutylmalonic, dibenzylmalonic, butyl (3,5-di-tert- butyl-4-hydroxybenzyl) malonic, bicycloheptenedicarboxy-

lic, etc.

Examples of the substituent G when it is a trivalent radical of a tricarboxylic acid, are radicals of the following acids: trimellitic, citric, nitrilo- triacetic, etc.

Examples of the substituent G when it is a tetravalent radical of a tetracarboxylic acid, are radicals of the following acids: butane-1,2,3,4-tetra- carboxylic, pyromellitic, etc.

Examples of the substituent G when it is a divalent radical of a dicarbamic acid, are radicals of the following acids: hexamethylenedicarbamic, 2,4-to- luylenedicarbamic, etc.

Compounds having general formula (VI) are pre- ferred, wherein G is hydrogen, G11 is hydrogen or methyl, n is 2 and Gl2 is a diacyl radical of an ali- phatic dicarboxylic acid having from 4 to 12 carbon atoms.

Specific examples of polyalkylpiperidines having general formula (VI) are: 1) 4-hydroxy-2,2,6,6-tetramethylpiperidine; 2) 1-allyl-4-hydroxy-2,2,6,6-tetramethylpiperidine; 3) 1-benzyl-4-hydroxy-2, 2, 6, 6-tetramethylpiperidine ; 4) 1- (4-t-butyl-2-butenyl)-4-hydroxy-2,2,6,6-tetrame- thylpiperidine;

5) 4-stearyloxy-2,2,6,6-tetramethylpiperidine; 6) 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperi- dine; 7) 4-methacryloyloxy-1,2,2,6,6,-pentamethylpiperi- dine; 8) 1, 2, 2, 6, 6-pentamethylpiperidin-4-yl-- (3, 5-di-t- butyl-4-hydroxyphenyl) propionate; 9) di (l-benzyl-2,2,6,6-tetramethylpiperidin-4-yl) ma- leate; 10) di (2,2,6,6-tetramethylpiperidin-4-yl) succinate; 11) di (2,2,6,6-tetramethylpiperidin-4-yl) glutarate; 12) di (2,2,6,6-tetramethylpiperidin-4-yl) adipate; 13) di (2,2,6,6-tetramethylpiperidin-4-yl) sebacate; 14) di (1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate; 15) di (1,2,3,6-tetramethyl-2,6-diethylpiperidin-4- yl) sebacate; 16) di (l-allyl-2,2,6,6-tetramethylpiperidin-4-yl) ph- thalate; 17) (1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl) ace- tate; 18) ester of tri (2,2,6,6-tetramethylpiperidin-4-yl) trimellitic acid; 19) l-acryloyl-4-benzyloxy-2,2,6,6-tetramethylpiperid- ine; 20) di (2,2,6,6-tetramethylpiperidin-4-yl) diethylmalon-

ate; 21) di (1,2,2,6,6-pentamethylpiperidin-4-yl) dibutyl- malonate; 22) di (1,2,2,6,6-pentamethylpiperidin-4-yl) butyl- (3,5- di-tert-butyl-4-hydroxybenzyl) malonate; 23) hexane-1', 6'-bis (4-carbamoyloxy-1-n-butyl-2,2,6,6- tetramethylpiperidine; 24) toluene-2', 4'-bis (4-carbamoyloxy-1-n-propyl-2,2,- 6,6-tetramethylpiperidine; 25) dimethyl-bis (2,2,6,6-tetramethylpiperidin-4- oxy) silane; 26) phenyl-tris (2,2,6,6-tetramethylpiperidin-4-oxy)- silane; 27) tris (l-propyl-2,2,6,6-tetramethylpiperidin-4- yl) phosphite; 28) tris (l-propyl-2,2,6,6-tetramethylpiperidin-4- yl) phosphate; 29) bis (1,2,2,6,6,-pentamethylpiperidin-4-yl) phenyl- phosponate; 30) 4-hydroxy-1,2,2,6,6,-pentamethylpiperidine; 31) 4-hydroxy-N-hydroxyethyl-2,2,6,6,-tetramethylpipe- ridine; 32) 4-hydroxy-N- (2-hydroxypropyl)-2, 2, 6, 6-tetramethyl- piperidine; 33) 1-glycidyl-4-hydroxy-2,2,6,6-tetramethylpiperid- ine.

(b) Compounds having general formula (VII):

wherein n is 1 or 2; G, G1 and Gll have the same meanings defined under point (a); G13 is hydrogen, a Cl-Cl2 alkyl group, a C2-C5 hydroxyalkyl group, a C5-C7 cycloalkyl group, a C7-C8 aralalkyl group, a C2-C18 alkanoyl group, a C3-C5 alkenoyl group, a benzoyl group, or a group having the following general formula: wherein G, G, and Gii have the same meanings de- fined under point (a); G14, when n is 1, is hydro- gen, a Ci-Cis alkyi group, a C3-C8 alkenyl group, a <BR> <BR> CS-C7 cycloalkyl group, a C1-C4 alkyl group substi- tuted with a hydroxyl group, with a cyano group, with an alkoxycarbonyl group or with a carbamide group, a glycidyl group, a group having the

formula-CH2-CH (OH)-Z or having the formula -CONH-Z wherein Z is hydrogen, methyl or phenyl; G14, when n is 2, is a C2-C12 alkylene group, a C6-C12 arylene group, a xylylene group, a group having the formula-CH2-CH (OH)-CH2-or having the formula-CH2-CH (OH)-CH2-0-D-0-wherein D is a C2-C10 alkylene group, a C6-cl5 arylene group, a C6-C12 cycloalkylene group; or, on the condition that G13 is not an alkanoyl group, an alkenoyl group or a benzoyl group, G14 can also be a l-oxo-(C2-C12)- alkylene group, a divalent radical of a dicarboxy- lic acid or of a dicarbamic acid, aliphatic, cycloaliphatic or aromatic, or also a-CO-group; or, when n is 1, G13 and G14 together can also be a divalent radical of a 1,2- or 1,3-dicarboxylic acid, aliphatic, cycloaliphatic or aromatic.

The term aryl refers to an aromatic hydrocarbon such as, for example, phenyl or naphthyl. The term aralkyl refers to an alkyl substituted with an aromatic hydrocarbon, for example, a hydrocarbon having from 6 to 10 carbon atoms; examples of aralkyls are benzyl, a-methylbenzyl, etc.

C1-C12 alkyl or Ci-ci, alkyl groups have already been defined under point (a).

C5-C7 cycloalkyl groups are, preferably, cyclohe-

xyl.

When G13 is a C7-C8 aralkyl group, it is phenyl- ethyl, preferably benzyl.

When G13 is a C2-C5 hydroxyalkyl group, it is 2-hydroxyethyl, 2-hydroxypropyl, etc.

Examples of G13, when it is a C2-C18 alkanoyl group, are: propionyl, butyryl, octanoyl, dodecanoyl, hexadecanoyl, octadecanoyl, etc., preferably acetyl and, when it is a C3-C5 alkenoyl group, preferably acryloyl.

Examples of G14, when it is a C2-C8 alkenyl group, are: allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexen- yl, 2-octenyl, etc.

Examples of G.,, when it is a Cl-c4 alkyl group substituted by a hydroxyl, cyano, alkoxycarbonyl or carbamide group, are: 2-hydroxyethyl, 2-hydroxypropyl, 2-cyanoethyl, methoxycarbonylmethyl, 2-ethoxycarbonyl- ethyl, 2-aminocarbonylpropyl, 2- (dimethylaminocarbo- nyl) ethyl, etc.

Examples of C2-C12 alkylene groups are: ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene, dodeca- methylene, etc.

Examples of C6-cl5 arylene groups are: o-m-or p- phenylene, 1,4-naphthylene, 4,4'-diphenylene, etc.

Examples of C6-C12 cycloalkylene groups are, preferably, cyclohexylene.

Preferred compounds having general formula (VIII) are those wherein n is 1 or 2, G is hydrogen, Gll is hydrogen or methyl, G13 is hydrogen, a Cl-Cl2 alkyl group or a group having the formula: and G14, when n is 1, is hydrogen or a Cl-Cl2 alkyl group and, when n is 2, is a C2-C8 alkylene group or a 1-oxo- C2-Ce alkylene group.

Specific examples of polyalkylpiperidines having general formula (VII) are: 1) N, N'-bis (2,2,6,6-tetramethylpiperidin-4-yl) hexa- methylene-l, 6-diamine; 2) N, N'-bis (2,2,6,6-tetramethylpiperidin-4-yl) hexa- methylene-l, 6-diacetamide; 3) Bis (2,2,6,6-tetramethylpiperidin-4-yl) amine; 4) 4-benzoylamino-2,2,6,6-tetramethylpiperidine; 5) N, N'-bis (2,2,6,6-tetramethylpiperidin-4-yl)-N, N'- dibutyladipamide; 6) N, N'-bis (2,2,6,6-tetramethylpiperidin-4-yl)-N, N'- dicyclohexyl-2-hydroxypropylene-l, 3-diamine;

7) N, N'-bis (2,2,6,6-tetramethylpiperidin-4-yl)-p- xylylenediamine; 8) N, N'-bis (2,2,6,6-tetramethylpiperidin-4-yl) succinediamide; 9) Bis 6,6- tetramethylpiperidin-4-yl)-p-aminodipropionate; 10) Compounds having the formula: 11) 4- [bis (2-hydroxyethyl) amino]-l, 2,2,6,6-penta- methylpiperidine ; 12) 4- (3-methyl-4-hydroxy-5-tert-butylbenzamido)- 2,2,6,6-tetramethylpiperidine; 13) 4-methacrylamido-l, 2,2,6,6-pentamethylpiperidine. c) Compounds having general formula (VIII):

wherein n is 1 or 2; G, Gl and Gli have the same meanings described under point (a); G15, when n is 1, is a C2-C8 alkylene or hydroxyalkylene group, or a C4-C22 acyloxyalkylene group, and, when n is 2, is a (-CH2) 2C (CH2-) 2 group.

Examples of G15, when it is a C2-Cs alkylene or hydroxyalkylene group, are: ethylene, 1-methylethylene, propylene, 2-ethylpropylene, 2-ethyl-2-hydroxymethyl- propylene, etc.

An example of Guis, when it is a C4-C22 acyloxyalkyl- ene group is 2-ethyl-2-acetoxymethylpropylene.

Specific examples of polyalkylpiperidines having general formula (VIII) are: 1) 5-dioxaspiro [5.5] un- decane; 2) 5-dioxa- spiro [5.5] undecane; 3) 8-aza-2,7,7,8,9,9-hexamethyl-l, 4-dioxaspiro [4.5]- decane; 4)

methyl-1,5-dioxaspiro [5.5] undecane; 5) tetramethyl-l, 5-dioxaspiro [5.5] undecane; 6) 2,2,6, 6-tetramethylpipridine-4-spiro-2'-(1',3'- dioxane)-5'-spiro-5"- (1'', 3"-dioxane)-2"-spiro- 4'''-2''',2''',6''',6'''-tetramethylpiperidine). d) Compounds having general formula (IXA), (IXB) and (IXC), the compounds having general formula (IXC) being preferred: wherein n is 1 or 2, G, G, and Gll have the same

meanings described under point (a); G16 is hydro- gen, a C1-C12 alkyl group, an allyl group, a ben- zyl, a glycidyl group or a C2-C6 alkoxyalkyl group; G17, when n is 1, is hydrogen, a C1-C12 alkyl group, a C3-Cs alkenyl group, a C7-C9 aralalkyl group, a C5-C7 cycloalkyl group, a C2-C4 hydroxyalkyl group, a Cz-C6 alkoxyalkyl group, a C6-C10 aryl group, a glycidyl group, or a group having the formula - (CH2) p-COO-Q or - (CH2) p-O-CO-Q wherein p is 1 or 2 and Q is a C1-C4 alkyl group or a phenyl; G17, when n is 2, is a C2-C12 alkylene group, a C4-C12 alken- ylene group, a C6-C12 arylene group, a group having the formula-CH2-CH (OH)-CH2-O-D-O-CH2-CH (OH)-CH2- wherein D is a C2-C10 alkylene group, a C6-C15 arylene group, a C6-C12 cycloalkylene group, or a group having the formula CH2-(OCH2-CH(OZ')CH2)2whereinZ'is-CH2CH(OZ') hydrogen, a C1-C18 alkyl group, an allyl, a benzyl, a C2-C12 alkanoyl group or a benzoyl; T1 and T2 are, each independently, a C1-C18 alkyl group, aC-C aryl group, a C7-C9 aralalkyl group, said groups optionally substituted with a halogen atom or with a C1-C4 alkyl group; or T1 and T2, considered jointly with the carbon atom to which they are bound, form a Cl-cl cycloalkane ring.

Examples of Cl-cl2 alkyl groups are: methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, etc.

Examples of C1-C18 alkyl groups are, in addition to those listed above: n-tridecyl, n-tetradecyl, n-hexa- decyl, n-octadecyl, etc.

Examples of C2-C6 alkoxyalkyl groups are: methoxy- methyl, ethoxymethyl, propoxymethyl, t-butoxymethyl, ethoxyethyl, ethoxypropyl, n-butoxyethyl, t-butoxy- ethyl, isopropoxyethyl, propoxypropyl, etc.

Examples of G17, when it is a C3-C5 alkenylic group are: 1-propenyl, allyl, methallyl, 2-butenyl, 2-penten- yl, etc. <BR> <BR> <BR> <P> Examples of G17, T1 and T2, when they are aC-C<BR> <BR> aralkyl group are: phenethyl, preferably benzyl.

Examples of cycloalkane rings, formed by T1 and Tz when these substituents are considered jointly with the carbon atom to which they are bound, are: cyclopentane, cyclohexane, cyclo-octane, cyclododecane, etc.

Examples of G.,, when it is a C2-C4 hydroxyalkyl group, are: 2-hydroxyethyl, 2-hydroxypropyl, 2-hydroxy- butyl, 4-hydroxybutyl, etc.

Examples of G17, T1 and Tz, when they are a C-C aryl group are: a-orS-naphtyl, optionally substituted

with a halogen atom or a C1-C4 alkyl group, etc.

Examples of G17, when it is a C2-C12 alkylene group are: ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, deca- methylene, dodecamethylene, etc.

Examples of G17, when it is a C4-C12 alkenylene group are: 2-butenylene, 2-pentenylene, 3-hexenylene, etc.

Examples of G17, when it is a C6-C12 arylene group are: o-, m-or p-phenylene, 1,4-naphthylene, 4,4'- diphenylene, etc.

Examples of Z', when it is a C2-C12 alkanoyl group are: propionyl, butyryl, octanoyl, dodecanoyl, prefera- bly acetyl.

Examples of D, when it is a C2-C10 alkylene group, a C6-C15 arylene group or a C6-C12 cycloalkylene group are defined above under point (b).

Specific examples of polyalkylpiperidines having general formula (IX) are: 1) 3-benzyl-l, 3,8-triaza-7,7,9,9-tetramethylspiro- [4.5] decane-2,4-dione; 2) 3-n-octyl-1,3,8-triaza-7,7,9,9-tetramethylspiro- [4.5] decane-2,4-dione; 3) 3-allyl-1, 3,8-triaza-l, 7,7,9,9-pentamethylspiro- [4.5] decane-2,4-dione;

4) 3-glycidyl-l, 3,8-triaza-7,7,8,9,9-pentamethyl- spiro [4.5] decane-2,4-dione; 5) 1,3,7,7,8,9,9-heptamethyl-l, 3,8-triazaspiro [4.5]- decane-2,4-dione ; 6) 2-isopropyl-7,7,9,9-tetramethyl-l-oxa-3,8-diaza-4- oxospiro [4.5] decane; 7) 2,2-dibutyl-7,7,9,9,-tetramethyl-l-oxa-3,8-diaza-4- oxospiro [4.5] decane; 8) 2,2,4,4-tetramethyl-7-oxa-3,20-diaza-21-oxodi- spiro 2] heneicosane; 9) 2-butyl7,7,9,9-tetramethyl-l-oxa-4,8-diaza-3- oxospiro [4.5] decane; and, preferably, 10) 8-acetyl-3-dodecyl-l, 3,8-triaza-7,7,9,9-tetra- methylspiro [4.5] decane-2,4-dione; or a compound having one of the following formulae:

(IX)-14.

(e) Compounds having general formula (X): wherein n is 1 or 2, and G18 is a group having one of the following formulae: wherein G and Gll have the same meanings described under point (a); G, and G2 are hydrogen, methyl, or together from a substituent =0, E is-0 or-NG13- ;

A is a C2-6 alkylene group or a- (CH2) 3-0-group; x is 0 or 1; G13 is hydrogen, a Cl-Cl2 alkyl group, a C2-Cs hydroxyalkyl group, a C5-C7 cycloalkyl group; G19 has the same meanings as G18 or is one of the following groups:-NG2lG22,-OG23,-NHCH2OG23 or -N (CH20G23) 2 G20, when n is 1, has the same mean- ings as G18 or G19 and, if n is 2, it is an-E-B-E- group wherein B is a C2-Cs alkylene group optional- ly interrupted by 1 or 2-N (G21)-groups; G21 is a C1-Cl2 alkyl group, a cyclohexyl group, a benzyl, a C1-C4 hydroxyalkyl group, or a group having the following general formula: G22 is a C1-Cl2 alkyl group, a cyclohexyl group, a benzyl, a C1-C4 hydroxyalkyl group; G23 is hydrogen, a C1-Cl2 alkyl group, a phenyl, or G21 and G22 together are a C4-C5 alkylene or oxyalkylene group, for example: or a group having the formula: G21 is a group having the general formula:

Examples of C1-Cl2 alkyl groups are: methyl, ethyl, n-propyl, n-butyl, sec-butyl, t-butyl, n-hexyl, n-oc- tyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dode- cyl, etc.

Examples of C1-C4 hydroxyalkyl groups are: 2-hy- droxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydro- xybutyl, 4-hydroxybutyl, etc.

Examples of A, when it is a C2-C6 alkylene group are: ethylene, propylene, 2,2-dimethylpropylene, tetra- methylene, hexamethylene, etc.

Examples of Gzi anf G22, when they jointly form a <BR> <BR> <BR> <BR> <BR> C4-C5 alkylene or oxyalkylene group, are: tetramethyl- ene, pentamethylene, 3-oxapentamethylene, etc.

Specific examples of polyalkylpiperidines having general formula (X) are:

wherein R is: wherein R is: wherein R is:

(f) Oligomeric or polymeric compounds whose recurrent structural unit contains a 2,2,6,6-tetramethyl- piperidine radical having general formula (V), in particular polyesters, polyethers, polyamides, polyamines, polyurethanes, polyureas, polyamino- triazines, poly (meth) acrylates, poly (meth) acry- lamides, and their copolymers containing said radical.

Specific examples of the above 2,2,6,6-polyalkyl- piperidines are represented by the following formulae wherein m is a number between 2 and 200:

wherein R is:

wherein m'and m''are an integer between 0 and 200 extremes included, on the condition that m'+ m"is m.

Further examples of light stabilizers which can be used for the purpose are: -the reaction products between compounds having formula (XII): and epichlorohydrin; polyesters obtained by the reaction of butane- 1,2,3,4-tetracarboxylic acid with a bifunctional alcohol having formula (XIII): (XIII) Whose carboxylic termination generated by tetra- carboxylic acid has been esterified with a 2,2,- 6,6-tetramethyl-4-hydroxypiperidine group; compounds having general formula (XIV):

wherein about a third of the R radicals represent a-C2H5 group and the remaining a group having the formula: and m is a number between 2 ans 200 extremes included; -copolymers whose recurrent unit consists of two units having the formula: a unit having the formula: and a unit having the formula:

(g) Compounds having general formula (XVIII): wherein G, G1 and Gll have the same meanings de- scribed above under point (a). Compounds having general formula (XVIII) wherein G is hydrogen and G1l is hydrogen or methyl, are preferably used.

Specific examples of compounds having general formula (XVIII) are: -2,2,6,6-tetramethyl-4-piperidone (triacetone- amine); 1,2,2,6,6-pentamethyl-4-piperidone; -2,3,6-trimethyl-2,6-diethyl-4-piperidone.

(h) Compounds having general formula (XIX):

wherein Gll has the same meanings described above under point (a) and G25 is a direct bond, a methy- lene or preferably a carbonyl, as described in German patent application DE 3,530,666.

(i) Compounds having general formula (XX): wherein R1 is a Cl-calo alkyl group, a C5-C12 cyclo- alkyl group optionally substituted with a C1-C4 alkyl group, a phenyl optionally substituted with a Ci-Cio alkyi group; R2 is a Cr-Cio alkylene group; R3 is a hydrogen, a C1-C8 alkyl group, 0', a-CH2CN <BR> <BR> group, a C3-C6 alkenyl group, a C7-C9 phenylalkyl

group optionally substituted in the phenyl radical with a Ci-c4 alkyl group, a Ci-c 8 acyl group; and ni is a number between 1 and 50 extremes included.

Specific examples of compounds having general formula (XX) are: <BR> <BR> <BR> (1) poly-methylpropyl-3-oxy- [4- (2,2,6,6-tetramethyl)- piperidinyl] siloxane, known under the trade-name of WASIL 299 of Great Lakes; (2) poly-methylpropyl-3-oxy- [4- (1,2,2,6,6-penta- methyl)-piperidinyl] siloxane.

The granular formula of the present invention can be combined, as specified above, with other convention- al additives or their mixtures. These additives are added in a quantity ranging from about 0.1% to 5% by weight with respect to the weight of the films based on polyolefins or olefinic copolymers to be stabilized, preferably between 0.5% and about 3% by weight.

Examples of other conventional additives which can be used are: antioxidants (such as, for example, alkyl- ated monophenols, alkylthiomethylphenols, hydroquinones and alkylated hydroquinones, tocopherols, hydroxylated thiophenyl ethers, alkylidene-bisphenols, benzyl compounds containing O, N or S, hydroxybenzylated malonates, aromatic hydroxybenzyl compounds, triazine compounds, benzylphosphonates, acylaminophenols, esters

of ß- (3,5-di-t-butyl-4-hydroxyphenyl) propionic acid with monohydric or polyhydric alcohols, esters of - (5- t-butyl-4-hydroxyphenyl) propionic acid with monohydric or polyhydric alcohols, esters of 9- (3,5-dicyclohexyl- 4-hydroxyphenyl) propionic acid with monohydric or polyhydric alcohols, esters of (3,5-di-t-butyl-4- hydroxyphenyl) acetic acid with monohydric or polyhydric alcohols, amides of ß-(3,5-di-t-butyl-4-hydroxyphenyl)- propionic acid; other ultraviolet-ray and light stabi- lizers (such as, for example, derivatives of 2- (2'- hydroxyphenyl) benzotriazoles, esters of benzoic acids, acrylates, oxamides, 2- (2-hydroxyphenyl)-1,3,5-tri- azine);"metal deactivators" ; phosphites and phosphon- ites; agents capable of destroying peroxides; basic co- stabilizers, nucleating agents; fillers and reinforcing agents; other additives (such as, for example, plastic- izers, emulsifying agents, pigments, optical brighten- ers, flame-retardants, antistatic agents, blowing agents, thiosynergizing agents); benzofuranones and indolinones.

The present invention also relates to a process for the stabilization of agricultural films based on polyolefins or olefinic copolymers, particularly useful for greenhouses, comprising the incorporation of the granular form of the present invention into the poly-

olefins or olefinic copolymers subsequently transformed into the above films. Greenhouses covered with the above agricultural films are a further object of the present invention.

Some illustrative but non-limiting examples are provided hereunder for a better understanding of the present invention and for its embodiment.

EXAMPLE1 50 g of Compound (b), corresponding to 2-hydroxy- 4-n-octoxybenzophenone, are charged into a 250 ml flask equipped with a magnetic stirrer and externally heated with an oil bath. The compound is melted (at 50°C) and subsequently heated to about 100°C; 100 g of Compound (a), corresponding to [2,2'-thiobis (4-t-butyloctylphen- olate)-n-butyl-amine Nickel (II)], are then added gradually.

Compound (a) dissolves in Compound (b) and, on heating to 120°C, a liquid mass is obtained, which is poured onto an aluminum plate cooled to about 0°C.

After about 1 hour, the solidified product is granulated by grinding, obtaining granules of the desired dimensions.

EXAMPLE 2 50 g of Compound (b), corresponding to 2-hydroxy- 4-n-octoxybenzophenone, are charged into a 250 ml flask

equipped with a magnetic stirrer and externally heated with an oil bath. The compound is melted (at 50°C) and subsequently heated to about 70°C; 100 g of Compound (a), corresponding to [2, 2'-thiobis (4-t-butyloctylphen- olate)-n-butyl-amine Nickel (II)], are then added gradually.

Compound (a) dissolves in Compound (b) and, maintaining a temperature of 70°C, a liquid mass is obtained, which is dripped onto an aluminum plate cooled to about 0°C. After 10-15 minutes, the drops solidify and granules of the desired dimensions are obtained.