may be a different polyester than that used as the main resin component of the polyester composition preferred quenchers which are present in the polyester concentrate of this invention are periodic table group i or group ii metal acid phosphates preferably in the form of the low hydrates preferred metals are group ii metals such as alkaline earth metals and zinc more preferred quenchers are calcium phosphate and zinc phosphate most preferably monocalcium or monozinc phosphate monohydrate and mixtures thereof the quencher may be mixed with the polyester resin to form a concentrate containing about 5 to 75 more preferably about 5 to 50 and most preferably about 10 to 30 by weight of the quencher based on the weight of the resin the concentrate u201c consists essentially of u201d a uniform mixture of the resin and quencher by which is meant that the concentrate does not contain any ingredients which are reactive with or can be made to be reactive with the quencher to form a discolored reaction product such as antimony oxide and or certain light colored pigments such as zinc sulfide the concentrate may however contain minor amounts of additional ingredients such as polymers other than polyesters stabilizers antioxidants and the like which do not react with and discolor the quencher concentrate the concentrate may be prepared by forming a uniform mixture of the polyester resin the quencher in powder form and other optional ingredients if any and passing a melt of the mixture through a mixer extruder to form pellets of the concentrate conventional single or double screw extruders may be used to form the concentrate mixture with a preferred temperature profile ranging from about 250 u00b0 to 280 u00b0 c from feed zone to die.